VOL. LXIX. Copyright, 1900, by the AMERICAN ARCHITECT AND BUILDING NEWS COMPANY, Boston, Mass. Entered at the Post-Office at Boston as second-class matter. THE 33 35 36 37 38 38 39 40 THE three hundred and fifty-one children attending one of the Jersey City public schools have recently had their eyes examined by a competent oculist, at the order of the School Board, and he reports that only sixty-nine of the number possess perfect eyesight. The statement is not a little startling, as the percentage of imperfection is very high, and those who read hastily probably feel that, as the defects are found in school-children, the cause of the defects must lie in the improper lighting of the school-rooms, and that the architect who designed the building is responsible for a physical infliction of very grievous nature. But it is not fair to make such a deduction, and, more than this, we do not feel that the diseases and weaknesses of the eyes that afflict school-children, defects that statistics show to be on the increase, are in the major degree chargeable to the improper lighting of schoolrooms, although it is the custom to make that charge as the easiest way of disposing of the matter. As to the large number of children in the Jersey City school reported as having eyesight defective at the time of the examination, it must be remembered that the eye, like other portions of the body, is subject to temporary ailments, and so an examination made a few weeks later would doubtless reveal that many natural cures had been effected meanwhile. School-children occupy school-rooms only some five or six hours a day, and during the morning session, at least, their physical condition is better than at any other time in the day, and so not likely to be much affected by improper lighting of the school-room. Moreover, scholars are occupied in recitation, during which the eye has chance of rest, from one-third to four-fifths of the entire time spent within the school-building, and it seems to us a gross absurdity to assert that the short period of actual study in the school-room, however poorly that may be lighted, is the cause, or even a chief cause, of the trouble. Statistics show that ocular defects are on the increase, and it would be interesting to know whether the ratio remains the same in the buildings which have been in use for a term of years, or whether the ratio increases while conditions of lighting, good or bad, have remained unchanged. The fact that eyesight is deteriorating, while, as every one knows, greater effort is made to secure the proper lighting of school-rooms than ever before, tends to show that something other than the school-room is at fault. The other probable causes are the typographical imperfections of the school-books used, the enlargement in the educational curriculum, which entails longer hours of study, but most of all, the improper attitudes which children are allowed to assume at home while reading and studying, and the lack of care and watchfulness on the part of parents to provide proper light for the inevitable evening tasks, tasks which have to be disposed of while the eye is tired and strained. Our own parental ex No. 1284. perience satisfies us that school-book publishers and the improper conditions for study at home are more clearly responsible for weak and defective eyes than the imperfections of the school-rooms and the lack of watchfulness on the part of school-teachers. BUT IT UT as publishers will use worn stereotype-plates, and as it is not to be expected that parents of all classes, living in houses and tenements of every grade, can provide perfect conditions for home study or understand how necessary it is to make sure that a child holds the book in a proper light and at a proper distance from the eye, a School Board can do no more sensible thing than place the school-children under the regular inspection of competent oculists. Mr. Gerhard, in the paper we published a week or two ago, establishes a very good case in favor of the introduction of the rain-bath into the schoolhouses established in localities which serve only the families of the tenement-dweller, and shows clearly how a physical cleanliness cannot but make more simple the task of keeping the atmosphere of a school-room sweet and clean. The medical examination of school-children which is enforced in Boston and in some of the schools in New York and Chicago has already proved its great usefulness in preventing the spread of contagious disease, and the installation of an inspecting oculist is but another step in the same direction. If architects should be called on to provide buildings for only physically clean and healthy children, we fancy they would be less often charged with being ignorant of how to light and ventilate a school-room. T is doubtful whether the plumber, the painter or the roofer is responsible for a greater fire-loss during a year one than the other, but between them their carelessness causes an immense loss, through the agency of the forgotten candle, the oily rag and the overturned brazier. The painter probably heads the list of delinquents, since to the peril of the oily rag he adds that of the naphtha-torch, though fortunately the practice of burning off paint has given way somewhat to the practice of dissolving it off with strong solvents. The torch, however, caused last week a rather unusual and interesting fire, the one that destroyed the Baptist church at Arlington, We call it unusual, for it seems to us a rather unnecessary piece of thoroughness to remove old paint from a church spire with a naphtha torch preparatory to giving it "three strong coats" of new paint. The case is interesting for several reasons. The trustee who authorized the painters to use the torch seems to have had a feeling that the process was hazardous, and it was his purpose to be personally on the scene with a Babcock fire-extinguisher for use in case of mishap; but, most unfortunately, he forgot to put in an appearance, and so there was no carbonic dioxide at hand to turn upon the first flame, which did not delay in getting firm possession of the spire, In the next thoroughly dried by the recent intense heat. place, although the authorities seem to have secured from the insurance companies a builder's permit which allowed them to make the proposed repairs without vitiating their insurance, the permit had run out before the spire was ready for painting, and no steps had been taken to secure an extension of it. In the last place, the insurance-policies contain the usual clauses prohibiting the use of naphtha on the insured premises. gether it looks as if the Baptist Society would lose not only its church edifice but also the seventeen thousand dollars for which it was insured, and, seeing how things have resulted, must now boards and build a new spire, if their painters were unwilling to feel that it would have been cheaper to strip off the old clapget rid of the old paint with scrapers and sand-paper. It seems possible that, in such cases as this, where a good deal of old paint is to be got rid of, the pneumatic sand-blast might be used to advantage. Mass. THE Alto HE matter of shade-trees is one that at this season always attracts attention, and in behalf of those which are suffering through the drought it is worth while to explain how a Toledo, O., man helps his trees to maintain a vigorous leafage. Having, by the use of a post-hole auger, discovered in what directions the main roots run, he sinks over them a length or two of drain-tile sunk vertically, the upper ends coming to within an inch or two of the sod, which can easily be made to drain into them, so that in case of natural rain or hose-watering the roots receive from a short shower or slight artificial sprinkling a greater benefit than would be natural if the water fell upon an unprepared surface. But shade-trees do not suffer alone from drought and insects. It is said that they are injuriously affected by the passage of the electric-fluid over wires and cables that may be strung through or beside their branches, and as proof of this fact the manner in which the trees on Third Avenue, Brooklyn, have been destroyed by the feed-wire of the Third Avenue trolley-line is adduced. That the electric-fluid, in a more dilute form than a lightningstroke, is injurious to trees we do not of our own knowledge care to assert, but it is perhaps likely. But, whether this be true or not, the electric-current is certainly the indirect cause well as outside, and some wicker baskets which could not endure handling are said to have had marked interest because of their form and the patterns developed in their weaving. INS of great havoc to our shade-trees at the hands of telephone, brotherhood may make it necessary to call in and re-coin our rail TH As all N sending out the programme for the various classes of its Schools now housed at One-hundred-and-ninth Street and Amsterdam Avenue, New York, the National Academy of Design announces the establishment of a new department, in which the arts of die-sinking and the designing of coins and medals are to be taught under the united auspices of the American Numismatic and Archæological Society and the Academy of Design. Now, although the currency of the country is once more on a metallic basis and the industry of the counterfeiting circulating medium more frequently than in the past, we cannot believe that very many artists can make a livelihood by becoming expert in producing dies for use in the Government mints, all the more that the Director of the Mint has always shown a marked preference for adopting the designs prepared by the official designers. But there is on the other hand a very promising career for those who can produce artistic designs for the medals which are growing in favor as prizes to be distributed by learned, artistic, philanthropic and other bodies which stimulate emulation and promote progress in many directions by the inauguration of competitive contests of one kind or another. Moreover, even if a student cannot turn his training to account as a working die-sinker or medallist, he would find it of help in the studio attached to some of the great industries which are earning an enviable reputation for American silverware. TH HAT portion of the public that has not the great good fortune to be included in one or another class of artists has always drawn amusement from the exhibitions of peevish self-complacency which so many artists-be they painters, HE ease and comfort with which life is sustained in the sculptors, architects or photographers-seem to take pride and Klondike region and in Alaska is one of several facts that pleasure in exhibiting. Whistler's exhibitions of caustic illgo to support the theory that some at least of what we are temper may be forgiven, since they generally have some shadow of an excuse, and are, moreover, so very amusing: pleased to consider the aboriginal peoples of this continent in reality migrated from Asia, crossing Behring Strait by aid of besides one cannot help feeling at times that, like the antics of a Mosaic miracle, perhaps, by boats, or over the ice. the mountebank, they have their real purpose as a means of adsorts and conditions of men are seeking their fortunes in the discover how far the artist really dares to follow the fakir. vertising the artist and his product, and one is interested to Klondike and, not finding them, are compelled to return afoot There is never any means of telling when this foible of the along the coast by the easiest trails, it is possible that some one of them, trained in ethnological research, may, during his festation, so far as reported, is to be found in the published list artistic temperament will next break out, but its latest manitramp, light upon traces of the passage of the progenitors of of prizes-gold, silver and bronze medals and honorable menthe Mayas of Yucatan, and so show how this people of strongly tions-awarded to artists exhibiting at the Paris Exposition. Asiatic type arrived on this continent. For the ethnologist it is fortunate that the early peoples did not carry their food Appended to the list of recipients is a remark to the effect that the absence from the list of certain names, which might natupacked in the ubiquitous "tin" which now so untidily discloses rally be supposed would have been included in one grade or the route of the modern emigrant, soldier or picnicker. But another, is to be accounted for by the fact that these unnamed while the Maya riddle awaits solution, a good many enigmas artists "informed the jury that they would not accept silver or of less age are being unriddled by the patient investigations of bronze medals." Could peevish self-complacency go farther! trained explorers; indeed there is every evidence that American archæology is attaining a rank of very considerable worth. jury to whose discriminating judgment he had voluntarily subThe artist, in the lordly way of his kind, seems to say to the Probably it can never reach the plane occupied by Egyptian mitted his product, "I have weighed and measured myself and and East Indian research, but it can no longer be sneered at the value can be expressed only in gold." This manifestation as unfruitful and uninteresting, as used to be the case. One of the latest results achieved by American explorers is in the had been made as a condition of acceptance at the time the exof conceit would have been merely amusing if this statement region of the Pajarito Cañon, between Bland and Española, hibits were placed before the jury of admission, but it is said New Mexico, where a party of explorers have discovered amidst "hundreds of similar ruins," the remains of a communal that the refusal - perhaps after all a quite uncalled-for one— building, two or three stories high, built of dressed stone, measwas announced to the jury after the posting of the list of goldmedallists. uring four hundred and fifty by five hundred feet and containing originally twelve or fifteen hundred rooms. Only one of these rooms was explored and the relics obtained are said to have been forwarded to the Northwestern University, at Evanston, Ill. If the report is true in all particulars, the finds are of great importance and, as the age of the ruins is placed at between five and six hundred years, they will compel the reconstruction of a good many theories regarding the civilization of the elder inhabitants of this country. In this one room, only nine feet by twelve, were found not only stone implements, battle-axes, polished stone mirrors and so on, but also iron knives and an iron bar, much rusted, of course, a rude smelting-furnace, copper ore and some gold ornaments, besides a beautiful turquoise. The fact that the clay pots about the hearth still contained bones and traces of food, such as scorched corn, together with other evidence, seems to indicate that the place was hastily deserted. The pottery, of which twenty-five samples were secured, was decorated on the inside surface as B EING modest persons, not given to placing undue value on the statements we make, we are, perhaps, too prone to feel the uselessness of correcting any immaterial blunder we may, from time to time, be guilty of, but we trust we have always shown a becoming willingness to correct any material misstatement likely to be of real prejudice to any one. There appear to be those, however, who flatteringly give an unexpected weight to our smallest saying and feel that even immaterial blunders should not go uncorrected. This agreeable flattery is to be found in the very opening paragraph of Number One, Volume First, of the Architect and Builder, a new architectural journal published in Philadelphia, where the editor points out that we accidentally did wrong to the memory of Leigh Hunt by ascribing to the late Clarence Cook the authorship of the verses dedicated to Abou Ben Adhem. We trust that in the long and prosperous career before him our contemporary may not find his pages sullied by a more direful blunder. PRISMATIC LIGHTING FOR THE ILLUMINATION OF DARK INTERIORS.1 HE practical application of the refractive property of the lens or prism to change the direction of lightrays passing through it, for the purpose of artificial illumination, originated with the French physicist, Fresnel, who first suggested its use in lighthouses, for the protection of maritime coasts, about the year 1815; and the Fresnel lens, in various modifications, is to-day solely used for this purpose. The Fresnel lens is designed for projecting a powerful beam of parallel light upon objects to be illuminated at a distance. The principle of this device is seen in Figure 1, which shows a central plano-convex lens surrounded by a series of rings or segments of lenses or prisms, to which successively diminishing curvatures or angles are given, in order to give them a common focus. Fig. 1. Within the past four or five years the application of this principle has been made, and with decided success, to the illumination of dark interior spaces, where the amount of light naturally entering therein is insufficient for satisfactory illumination, and artificial lighting must occasionally or constantly be resorted to. The requirements of public buildings and modern office-buildings, in this respect, have been most urgent, and the various devices known generally by the name of "prismatic lights" have been extensively used for the purpose and have proved so useful that in one or another form they have come to be regarded by architects and builders, not to speak of a great number of householders, as indispensable. It is the purpose of this communication to give a brief review of the art of prismatic lighting, which, at the present time, is passing through the active stages of the course of evolution, to which all the arts are subject, in determining the survival of the fittest. Omitting, for the present, c consideration of the vault-light for basements and cellars, where but one form of prism, namely, an approximately right-angled prism depending on total reflection for its utility, is admissible, there are two general methods in vogue of installing prismatic lights to meet the requirements of service. In the In one of these, the sheet of prismatic glass is placed in a window-frame in the vertical position, thus taking the place of the window-light. other, the sheet of prismatic glass is installed in a more or less inclined position, projecting outwards from the windowopening. This form of construction is known in the trade as a "canopy.' 99 The question as to which of c these two forms of installation will give the best results is determined by the extent of the sky-opening upon which dependence must be placed for light. Where this is of considerable area, as, for example, where the windows face a wide street, the prismatic glass set into the window-frames in the vertical position will give satisfactory results. B Fig. 2. B Fig. 3. Where the windows receive their light from a restricted area, as, for example, in courtyards or the side-yards of dwelling-houses, and generally in the many situations where high walls rising in close proximity cut off the free access of light from above, the projecting, canopy, form of prismatic glass is preferable. Speaking in a general way, the change from the vertical to the canopy form of installation will be indicated when the incident angle of the light falling on the window-opening averages 60 degrees from the horizontal plane. 1 Paper read by Dr. Wm. H. Greene, before the Franklin Institute, and printed in the Journal of the Society. | The popularity achieved by the use of light-projecting devices of this general nature has called into existence a great number of patented inventions, some claiming special forms of prism-construction (in combination, in certain cases, with a prismatic or lenticular formation on the reverse side of the glass), and of a far greater number of design-patents and methods of glazing, and other matters of minor detail. For the purpose of this communication, these minor devices may be left out of consideration, and the several generic forms of prismconstruction only will be given attention. These may be divided into two general classes: (1) Those in which the glass forming the light-projecting device consists of sheets having on one surface a series of prisms or segments of lenses of any desired angle, the back of the sheet being a plane surface, and (2) Those in which the glass forming the light-projecting device consists of sheets having on both surfaces a series of prisms or lenses. The prism-glass most generally known and used is that of the first-named class. The action of a section of prism-glass of this construction is shown in Figure 2, in elevation and plan. It is obvious that the general refracting effect of the prismatic surface in this and in the other forms of prism-glass will be substantially the same, whether the refractive surfaces of the structure be straight (i. e., prismatic), or more or less curved (i. e., lenticular), irrespective of the angles of the prism-sections or of the curvature of the lens-segments. It is important, however, that these angles (or curves) be carefully considered, since upon the correct appreciation of this element the light-projecting efficiency of the structure largely depends. Improper angles (or curvatures) may greatly diminish the efficiency of the device, by the dispersion and loss of light, caused by total reflections in the interior of the glass. There is general misapprehension regarding the proper action of light-projecting glass, which needs a word of reference. It is assumed by many that the prismatic light should be so constructed that all the exterior light transmitted from the interior boundary of the prismatic window, or canopy, b should be directed in lines substantially parallel to the boundary-walls, floor and ceiling of the apartment, and that the more nearly this condition is realized the closer will be the approach to the theoreticallyperfect mode of operation. Some of the manufacturers of prismatic glass endeavor to realize this condition by varying the angles of the prisms uniformly from the centre to the edges of the sheets, on the principle of the Fresnel lens. A little consideration of what is intended to be realized by prism-lighting of interiors will suffice to show that this view is an erroneous one and liable to result, in practice, in a much inferior interior illumination than can be otherwise obtained. This criticism will be understood by stating the general proposition, that the objects of prismatic lighting are, first, to direct as much extraneous light into the interior as possible, and, second, to direct it in such manner as to derive the largest possible benefit therefrom. In considering the relative merits of parallel and divergent light-transmission by prismatic glass, it should be said that practically as much extraneous light can be directed into the interior space to be illuminated by the one as by the other arrangement of prisms or lenses. But, when we come to consider the second portion of the proposition, it can easily be shown that the system of transmitting the light in parallel lines cannot possibly be as effective as the method of divergent transmission, and more especially, divergent transmission in both vertical and horizontal planes, and for the following reason: It is well known that the best effects in interior illumination are realized when uniform diffusion throughout the apartment is obtained. This effect can be secured most effectively only when all shadows are obliterated by calling into requisition the action of the entering light reflected from all parts of the side-walls, floor and ceiling of the apartment. By the method of directing the transmitted light in parallel lines, the ill effects of shadows cast by opaque objects in the path of the entering light will be realized in the extremest degree, as there will be no ameliorating influence to counteract and neutralize the shadows by reflection from the bounding-walls and floor of the apartment; and an inspection of the condition of an apartment thus treated will disclose this objection at once. By the method of divergent transmission, while quite as much, or more, extraneous light is thrown into the apartment as by the other method, its distribution is decidedly more advantageous, from the fact that the repeated reflections from the bounding-surfaces of the apartment cause the practical obliteration of all shadows and a practically uniform diffusion of the light to all parts of the interior. Returning now to the descriptive portion of the subject, the modus troduced into the dark interior by the lateral collecting action of this device is so much clear gain over the devices previously described. Further consideration will show, also, that if the interior surface of the glass be provided with prisms of uniform angle, determined in each case by the length of the apartment to be illuminated, this form of construction will secure the same advantage in respect of the vertical diffusion of the entering light as will be obtained from the lenticular prismatic construction previously described. On theoretical grounds, therefore, the last-described modification of light-projecting glass, belonging to Class 2, should give the best results if intelligently installed. Comparative practical tests also bear out this conclusion. An additional and important advantage possessed by prism-glass of the last-named construction (namely, a prism-plate constructed with prisms on one side and prisms or lens-panels arranged transversely on the reverse side) remains to be noticed. Since all illumination by means of prism-glass is thrown from a a operandi of the simplest form of a light-projecting prismatic window is shown in the plan-views in Figure 2, A and B, in which the light from an exterior source falling upon the plane, outward surface of the glass is refracted at the boundary of the interior prismatic surfaces and projected into the room to be illuminated. Figure 2 A, which is a plan-view of this construction taken on the line a b, exhibits the effect of the light-distribution in vertical plane from the effect of refraction from the terminal portions of the prism, where the influence of the more oblique rays is not counteracted by a modification of the angles of the prism from the centre-line to the upper and lower edges of the glass. Figure 2 B is a plan on line c d, showing that the light-rays are not distributed divergently in the horizontal plane, but are all directed in parallel lines. Figures 3 and 4 represent the action of prismatic glass of the second class, i. e., in which both surfaces are prismatic or lenticular. Figure 3 shows a form of light-projecting glass that has lately come into use, and for which certain advantages are claimed over the construction previously described. The sheets in this form of prism-glass have one surface furnished with prisms-commonly placed toward the room to be lighted - and the other surface formed of a series of lenses of small curvature, distributed in panel form, parallel to the direction of the prisms. This construction, as well as that shown in Figure 2, manifestly exaggerates in the vertical plane the divergent distribution of the transmitted light, and consequently operates, so far as it goes, in the correct manner, utilizing the reflecting action of ceiling and floor in diffusing the light. The construction shown in Figure 3 possesses one obvious advantage over the several modifications of Class 1, namely, that the lenticular form of exterior surface arrests and directs into the dark interior to be lighted a certain amount of the exterior light, which, with the plane exterior surface of Class 1, would be lost by total reflection from the exterior plane surface. Practically, all of this additional light thus projected into the dark interior would be gained if the angle of the prism and the curvature of the lens-panels were correctly adapted to the length of the apartment to be lighted. The latest modification of Class 2 remains yet to be considered. In this, the interior prismatic surface of the glass is the same as that just described, but the exterior lenticular panels are arranged not parallel, but transversely, to the direction of the prisms. The details of this form of construction are shown in Figure 4, A and B, while the modus operandi is best observed in Figure 5, A and B. The radical difference in the operation of this form of light-projecting glass and that of both forms previously described resides in the fact that the light-distribution in this form is exaggerated in the lateral as well as in the vertical plane. This feature is illustrated in Figure 5 B, in which B is supposed to be a section of the prismatic glass taken on the line c d, from an inspection of which it will be manifest that the vertical arrangement of the exterior lenticular panels will serve a similar purpose in this construction in relation to the light falling sidewise on the exterior surface of the glass as the lenticular panels in the previous case serve in relation to vertical rays; namely, to arrest and refract into the dark interior a considerable amount of light in the horizontal plane which would otherwise be lost for useful purposes. All of the light thus collected and in | Fig. 5. comparatively low point, namely, through windows, while all other artificial illumination is directed from a point above, the shadows produced by the prisms on objects in a room constitute a disadvantage common to most systems of lighting by means of prisms, as has been noticed in what has preceded. The light-projecting glass last described, however, by reason of its diffusing quality, both in the horizontal and vertical planes, largely overcomes this objection. Where two such prism-windows are used for the same apartment, the light thrown from one window completely overlaps that thrown from the other, thereby practically obliterating the shadows produced by prism-lights of other constructions. This construction also has the advantage of enabling manufac turers to produce more readily the larger sizes of prisms, from the fact that one surface has projections at right angles to projections on the reverse side, giving a bridge effect, thus adding to the strength of the plate. For this reason, likewise, it is not essential to have the thickness of the body of the glass as great as with other forms; and, inasmuch as there is a larger loss of light, through absorption in passing through a thick than a thin medium, the loss of light from this cause may be very much reduced. Finally, it may be said that all the various forms of light-projecting prismatic glass accomplish, measurably, their intended purpose of considerably increasing the illumination of dark interiors over what would occur without artificial aid. In the selection of the kind of light-projecting glass and the manner of its installation, the user should be guided by the personal observation of the effects produced, rather than by the claims of rival manufacturers. THE CHANGES OF THE GREAT LAKE LEVELS. Picture Show-case for the Russian Navy Department. From Stroitel. A MONG old sailors and engineers who have studied Lake Michigan for fifty years, Captain Keith's discovery that the drainage-canal has lowered the lake level 5 inches does not produce much consternation. Lake Michigan, like all of the Great Lakes, is a mystery. Old seamen recall the fact that Lake Michigan once rose up bodily 7 feet in an hour along this coast. In 1886 it fell 3 feet in two hours. There was a great tidal wave in Lake Erie in 1843 at Buffalo, which drowned twenty people in their beds. So strange and unaccountable are the fluctuations in the levels of all the Great Lakes that sailors have an abiding faith in "Old Sub," the underground monster, who turns the water off and on in a subterranean passage under the lake. "Old Sub's tinkerin' with the stopcocks," say the seamen, when the water begins to creep up on the gauge. Sometimes the level goes lower and lower, and then the talk is that "Old Sub has taken to drink." Some believe that a great undiscovered passage exists between the Great Lakes and a body of open water about the North Pole, and that a disturbance there accounts for the wonderful ebb and flow of the water in the basin of the Great Lakes. Occasionally, on a trip to Waukegan some sailor announces that the boat passed over the very region where "Old Sub" is turning the water in, ice cold and in unlimited supply. In a little different way scientists have sometimes upheld the theory of a subterranean passage, which feeds the lakes, and cite the seven years' rise and fall of lake levels as a proof of it. Others take no stock in the theory of periodical movements. But through it all there is the mystery which has not been fathomed yet by any plummet or measured by the rise and fall of any barometer. Long before the opening of the drainage-canal a variation of 5 inches in the lake level was known to be an ordinary affair. Sometimes the variation can be accounted for, but more often it cannot. Scientific men are as much at a loss as the veriest old salt. Day in and day out the lake level changes aside from changes caused by the winds. No man knows why, and no man can reckon the times and the places of these lake "tides." So constant are the fluctuations that a general fall of 3 inches a year over the entire surface of Lake Michigan and Lake Huron would not be appreciable in the ordinary set of gauge readings. The automatic gauge shows an oscillation of the lake every twenty minutes, amounting sometimes to between 2 and 3 feet. In 1886, after the water had run down suddenly 6 feet in Chicago Harbor, an attempt was made to account for these oscillations on a scientific basis. Seven gauges were set about the lake and read at five-minute intervals. The upshot of it was that some of the observers decided that the phenomenon was due to a swing of the lake in its bed from shore to shore. Others did not think this reasonable, but had no better theory to advance. More remarkable still, it was found that one day's observations showed a general lowering over the whole of Lake Michigan of several inches. As early as 1673 Father Marquette took note of changes in the lake levels. He asked the Indians about it, and they said that Lake Michigan swung from high to low and back again in fourteen years, or that every seven years the water ran the gamut. Baron La Hontan, in 1689, made some tolerably extensive notes on the variations in lake levels. He wrote that in twenty-four hours once, at the northern extremity of Lake Michigan, he saw the lake rise 3 feet and fall 3 feet in the day. He was first to observe the flow of water from Lake Huron to Lake Michigan, or from Michigan to Huron, which is now acknowledged. "We cast our fishing-nets in the straits," says the doughty old explorer, "and for three days the current sucked them to the eastward so strongly that we could with difficulty haul them from the water. Then for two days the current set steadily toward the west, and carried our nets in that direction." Stories of mysterious inundations by the lake, of times when the beach widened, and a great fringe was added to the sand along the shore, have always been current among Indian tribes. From Marquette, down to engineers and seamen of to-day observation has confirmed these legends. At Sault Ste. Marie, General Dearborn noted an ebb and flow of 1 feet of water in two and a half hours. Lake Erie has been known to rise from 7 to 20 feet in a few hours. A few years ago, at Cleveland, the lake suddenly rose 5 feet. In 1886 Lake Michigan rushed up to a height of 7 feet above the ordinary level at Milwaukee. In that year the water fell 6 feet in Chicago Harbor, and somewhat less in the lake within a few minutes. High-masted schooners careened to one side, and the big poles knocked together confusedly. It looked as if the Chicago River would be drained dry in half an hour, and the experience has never been forgotten among the Chicago seamen. In 1848, it is said, the same thing occurred. In addition to these sudden and inexplicable changes in the lake level, there is a tolerably well-defined periodical movement of the surface extending over a number of years. Sometimes it is claimed that this movement requires seven years, sometimes ten years. Ossian Guthrie and others declare that the movement is not periodic, but that it usually extends over from two to ten years. Then there is an annual rise of the lake from January to June, caused by the ordinary spring rainfall, which runs the level of the lake up about one foot higher in June than in January. For thirty years consecutively the spring rise was found to be 14 inches. A series of heavy spring rainfalls will raise the level of the lake 3 or 4 feet above datum for a number of years, and a series of droughts will reduce it correspondingly. Beginning with 1847, Ossian Guthrie has kept a record of the fluctuations of the level of Lake Michigan. In 1847, as has been stated, Lake Michigan went very low. From 1847 to 1859, with occasional lapses, it crept up nearly 3 feet above datum. From 1859 to 1863 it fell, then it swung back to 24 feet above datum in 1876, ran down in 1879, going up abruptly in the spring of 1880. From 1880 to 1886 the lake level rose 3 feet. From 1886 to 1892 it fell about 4 feet. In the spring of 1893 it rose 15 inches in a few days' time. Since 1893 the lake has been going down, and during most of last fall and this spring it has been below the 1847 mark. To-day, owing to the usual rise from rainfalls, the lake is higher than it was before the opening of the drainage-canal. Figures at the United States engineer's office show that during January, February and March the lake level was just about what it was in December of 1899, although each day's record shows a variation of several inches. On January 11 there was a variation in the lake level of 1 foot. From February 11 to February 12, in 1894, the lake level at the foot of Randolph Street rose a little over 2 feet. These daily fluctuations of from 6 inches to 2 feet are accounted for, engineers believe, by winds and by barometric pressure. A strong east wind will easily raise the surface of the lake here 2 feet. Again, if the atmospheric pressure all over the surface of Lake Huron is suddenly reduced, the water will rush through the straits from Lake Michigan, and Huron will rise, mysteriously perhaps, on a perfectly calm day. Engineers at the office of the Drainage Board estimate that if no rainfall were to reach Lake Michigan, and the maximum flow of 300,000 cubic feet of water drawn off through the drainage-canal, it would take a little over eight years to reduce the level of Lake Michigan 1 foot. As a matter-of-fact, the annual rainfall always produces a waste overflow past Niagara which greatly exceeds that drawn off by the drainage-canal. If the water were not taken through the canal it would go over Niagara during spring freshets. In general, engineers agree that the physics of Lake Michigan and of all the Great Lakes has never been studied accurately, and that the mysterious movements of the immense inland seas offer a comparatively unworked field for useful and scientific research.- Chicago Inter-Ocean. MONIER CONSTRUCTION.1 Picture Show-case for the Russian Navy Department. From Stroitel. HE writer welcomes every proper form of popularization of engineering and architectural constructions in cement and steel in combination. But he thinks it will greatly advance the practice of this new system if it is relieved from the burden of a proprietary name and from the sus picion of being a patented system. It can be easily shown that any one is at liberty to employ steel and concrete in combination in almost any way he chooses, without infringing any fundamental patent. There are a few patents upon particular combinations of steel and concrete which may be made to hold, but these can be avoided if one so desires. As to Monier's claims, they seem to the writer to be practically nil, so far as priority of use is concerned. Neither does it appear that any American patent on this system has ever been taken out. It seems that Mr. W. E. Ward, Member of the American Society of Mechanical Engineers, of Port Chester, N. Y., was the first to use iron or steel in combination with concrete in a thoroughly scientific manner. In a paper before the American Society of Mechanical Engineers at the Cleveland meeting, in June, 1883, Mr. Ward described at length the construction of a residence wholly of reinforced concrete, which he designed and built in 1875.2 He says he began his experiments to this end in 1871, and began He claims the "invention" of this planning for these in 1867. system of construction, but has freely given it to the public, apparently never having applied for a patent upon it. In France, lettersof Iron and Concrete," so that Monier's use of wire-netting in conpatent were granted in 1869 to François Coignet on a "Combination crete for the manufacture of large vases (for orange trees) and small tanks, in 1876, loses all significance. Furthermore, Monier was a gardener and used his wire-netting in the body of his concrete merely to bind it firmly together and to prevent cracking. He had no knowledge of the stresses in a beam, and the use of the iron to resist the tensile stresses while the concrete is relied on to resist the compressive stresses. Thaddeus Hyatt, also, in his work on "Conkaldy, London, in 1876 and 1877. Both Hyatt's book and Ward's crete-Iron Construction," 1877, reports tests made for him by Kirpaper seem to have dropped out of notice. Hyatt seems never to have heard of Monier. It is Ward in America and Hyatt in England, therefore, to whom credit is due for a scientific combination of these materials. Hyatt acknowledges that the combination is not intelligently combined in building-construction. new, but claims that these two materials had not previously been The reason this system came to bear Monier's name is because it was patented and exploited in France and Germany under this name, and has now been brought here from Germany. The Monier construction proper seems to be adapted only to circular tanks and to arches symmetrically loaded. Where bending-moment has to be (imbedded wire) construction that it should no longer bear his name. resisted, the adaptation required is so different from the true Monier It should more properly be called cement-steel, or steel-cement, construction. placed solely upon the adhesion of the concrete to the wires, they When plain wires or rods are used, reliance being have been told that this has been the case in the Studebaker Buildare sure to work loose if there is much jar or variation of stress. I ing, Chicago, to such an extent as to necessitate the replacing of 1 Discussion by Mr. J. B. Johnson of a paper at the meeting of the Western Society of Engineers and published in the Journal of the Society. See Proceedings of the American Society of Mechanical Engineers, Vol. IV, page 388, and the American Architect for August 18, 1877. |