Selective absorption of solar energy. - Professor Langley publishes an extended, elaborate, and exceedingly important paper on the selective absorption of solar energy, as determined by observations with the spectro-bolometer at Allegheny observatory, and upon the summit of Mount Whitney. It consists mainly of a statement of results, with comparatively little detail, perhaps in some cases not quite so much as would be desirable in order to enable the reader to judge how far the numerical conclusions are to be trusted, since probable errors are seldom given. Further papers are promised, however, in which these matters are to be more fully treated. Prof. Langley's observations cover all the spectrum from about wave-length 0.35 in the ultra-violet to 3.00 in the infra-red, - far below the limit reached by any other investigator. The principal results are the following: 1. The maximum of energy in the diffraction spectrum is near the luminous maximum between the red and yellow, though varying with the sun's altitude. 2. Our atmosphere produces an enormous systematic absorption, increasing continually from the infra-red extremity of the spectrum, where it is comparatively slight, to the ultra-violet, where it is very great. This, however, is not to be taken as denying the existence of remarkble absorption-bands in the infrared. The observations, in fact, show four such bands at wave-lengths 0."94, 1."14, 1."37, and 1."83, each of them quite as remarkable as the great line A, near the lower extremity of the visible spectrum. 3. The character and color of the sunlight is markedly changed by the atmospheric absorption; so that, to the naked eye placed outside our air, the sun would appear decidedly bluish. 4. The solar constant indicated by the observations is even higher than Forbes's value: it rises to 2.84, and seems not unlikely to reach 3.00. (The units in which the solar constant is here expressed are not calories per square metre per minute, but ten-thousandths of a calory per square centimetre per minute.) 5. The apparatus used was so delicate that all the principal Fraunhofer lines of the visible spectrum showed themselves in the galvanometer readings. 6. The ratio of the luminous to the dark heat is greatly changed by the atmospheric absorption, being much greater outside our atmosphere than within it. The writer adds, "It is probable, however, that the solar spectrum before absorption, though probably weak below the red, yet extended very much farther into the infra-red than our charts indicate. We may even regard it as probable that some agent of the atmosphere acts as an almost complete barrier to the entrance or departure of rays below the point charted." The salient features of the investigation are the exquisitely sensitive apparatus devised for its prosecution, and the new method of deducing the solar constant from pyrheliometer observations at the earth's surface by means of separate co-efficients of transmission determined for radiations of different wave-lengths. An interesting question arises, also, as to the way in which our atmosphere acts to retain the sun's heat on the earth, in view of the observed fact, that, contrary to all previous suppositions, the air is more transparent to the red and infra-red rays than to those in the upper part of the spectrum. It would seem, as the author suggests, that the air must be almost opaque to rays of wave-lengths below some limit; that limit, however, being below the extreme point reached by his measures. — (Amer. journ. sc., March.) C. A. Y. [532 MATHEMATICS. Algebraical curves. — M. Noether seeks to establish a thoroughly rigorous foundation for the general theory of algebraical curves in space, and, to this end, proposes to investigate all of the fundamental properties of such curves as can be derived from the general theory of algebraical functions. References are given to the most important papers which have already appeared on this subject; and the author remarks that but two processes have been employed in these earlier papers. The first, developed principally by Cayley, depends upon the representation of these curves by a cone and a 'monoid:' the second seeks to apply the theory of algebraical functions directly to groups of points on the space-curve. The author uses both of these processes; founding them, however, upon firmly established and constantly valid theorems concerning algebraical functions, and shows that the first method, although leading to very general results, is not sufficient for a rigorous establishment of the entire theory. The limits of applicability of the second method are also indicated. The curves treated are without multiple points; and, since they are regarded as general intersections of surfaces, these surfaces can have no multiple points, nor can they have contact along a curve. The first part of the memoir treats of special cases of intersections of surfaces; and the second part, of the intersections of surfaces in general, these surfaces being conditioned only by the fact that they must contain the space-curve under consideration, be destitute of multiple-lines, etc. This general theory has inversely its most general application in the development of the geometry of special surfaces. A brief section is devoted to this latter subject, which the author proposes more fully to develop in a forthcoming paper. The present paper is undoubtedly a most important addition to the existing literature of algebraical space-curves. (Journ. reine und angew. math., xciii.) [533 T. C. -- Orthogonal surfaces.-M. Bianchi announces a theorem concerning certain triple systems of orthogonal surfaces; viz., all surfaces of constant negative curvature, R, give rise to a triple system of orthogonal surfaces, of which one system is formed of surfaces having the same constant negative curvature, and the other two of surfaces which have circles of radius, R, as one of the systems of their lines of curvature. An application is given to the surface formed by the revolution of the tractrix; the Cartesian co-ordinates, x, y, z, of a point in the corresponding triply orthogonal surfaces, are given in terms of three parameters, u, v, w; and the method of generation of these surfaces is described. (Atti della r. acad. dei lincei, vii.) T. C. [534 On Fuchsians.-M. Poincaré, in a series of memoirs presented to the French academy, has treated certain new functions, which he calls 'Fuchsians,' 'Kleinians,' 'theta-Fuchsians,' and 'zeta-Fuchsians.' These functions have a certain analogy to the elliptie and Abelian functions; viz., while these latter functions afford integrals of certain algebraic differentials, the new functions afford means of integrating linear differential equations with algebraic co-efficients. In the present paper the author merely introduces the subject by studying certain properties of Fuchsian groups (groupes Fuchsiennes), and expresses the intention of returning later to the study of their consequences from the point of view of the theory of functions. A fuller account of M. Poincaré's paper will be given later, the present brief notice being taken New method of determining specific gravity of solids. Professor Munroe, having occasion to ascertain on shipboard the specific gravities of samples of coal, and being prevented by the motion of the vessel from using the balance, devised a procedure which not merely served his purpose, but is susceptible of wide application. Placing a block of coal in a liquid so dense as to float it, he gradually reduced the density by the admixture of a lighter liquid, until the coal floated immersed. The homogeneity of the mixture being maintained by stirring, this equilibrium was, of course, reached only when the specific gravity of the liquid became equal to that of the immersed solid. He then measured the specific gravity of the liquid with a common hydrometer. For the notation of the lighter coals, he used a thick solution of canesugar; for anthracite, strong sulphuric acid. As a test of the accuracy of the results, he afterward repeated the determinations with Jolly's balance, obtaining, Difference. .004 + .009 .000 + .006 .000 .009 .001 +.004 [537 Domestic thermometry. — M. Gaston Tissandier considers the errors that are likely to be made in determining the temperature of a room by the usual method of a thermometer hung on the wall. He found that the apparent temperature of a closed room varied from 16° to 21.75°, according to the position of the thermometer. The air in the upper part of the room was much warmer than that near the floor, and the window had a very marked effect on the temperature of the air in its vicinity. These observations were made with tested thermometers. The errors made with the ordinary domestic thermometer are, of course, much greater. In order accurately to obtain the temperature of a room, M. Tissandier advises the thermometer to be held at the height of a man for about two minutes at several different points, and the mean of these obser. vations to be taken. - (La Nature, No. 508.) C. B. P. [538 describing experiments conducted by him on the value of the B. A. unit of resistance. Three series of observations were taken, two by Lorentz's method, and a third, in which the induction coils were separated from the disk so far that the result was practically independent of the radius of the coils. The mean value obtained was 1 B. A. unit = .98677×109 (c. G. s.). The standard of time was a tuning-fork, whose absolute pitch was determined by a new method. — (Electrician, Feb. 10.) J. T. [539 Pressure and resistance in carbon.-S. Bidwell read a paper before the Royal society, giving the results of experiments on carbon cylinders making contact at right angles with each other. He proves that changes in pressure produce the greatest proportional effect when the pressure and strength of current is comparatively low; on the removal of the pressure, the resistance returns to about its original value. The passage of a current the strength of which does not exceed a certain limit causes a permanent diminution of the resistance. Similarly, the lessening of resistance due to pressure is magnified by the action of the current. J. T. ENGINEERING. [540 Mr. William An The Antwerp water-works. derson recently read a paper at the Institution of civil engineers in London, which contains some interesting facts in regard to the purification of water for domestic purposes. Antwerp has 200,000 inhabitants, and until recently its water was derived from shallow wells and from open canals. The well-water, though clear to look at, was for the most part dangerously contaminated by the sewage. The new works take the water from the Nèthe at a point eleven miles from Antwerp. This water was very impure, even after ordinary filtration through sand, as the river flowed through a highly cultivated country, carrying up the drainage of Malines on the flood-tide, and bringing down that of the villages on its upper waters on the ebb. The time during which water could be taken was thus limited to about three-quarters of an hour in each tide. Prof. Bischoff, Dr. Frankland, and Mr. Hatton had shown that finely divided metallic iron had the power of destroying organic impurities, removing color, separating finely suspended matter, and, above all, destroying the germs of putrefaction, of bacteria, and probably those of epidemic diseases. To confirm the laboratory evidence, a pair of filters with a total area of 680 square feet was made at Waelhem; the first filter being placed upon a higher level than the second, and filled with a bed of spongy iron and gravel, mixed in the proportion of one to three, covered with a layer of ordinary filter-sand. In this filter the water would become charged with iron, to eliminate which it was to be exposed to the air, and passed through a second or common sand-filter, in which the red oxide would be deposited. Three months of trial proved so satisfactory that three filters of the same kind were made, having an aggregate area of 31,000 feet, with three sand-filters of the same area. Eighteen months' work has shown that the water remains clear and bright, while the spongy iron showed no signs of deterioration. Dr. Frankland reports favorably upon the chemical condition of the water, and also upon the complete destruction of bacteria and their germs.(Van Nostrand's mag., March, 1883.) G. L. V. [541 Seasoning wood for musical instruments. Mr. C. René of Stettin has devised a process for the drying of wood, intended especially for the prepara tion of wood for musical instruments, but perhaps otherwise useful. It is described as follows: The wooden boards are so arranged in a large iron kettle that gases may freely circulate over their entire surface, and exposed, in the first place, for twelve hours, to the drying effects of hot air. After this the kettle is closed, reheated by the apparatus below, and the air exhausted, when the kettle is filled with oxygen ozonized by electrical sparks passing continually between two points of platina, forming the end-poles of two wires conducted through tubes of glass into the kettle. The ozone is said to act so energetically upon the heated wood, that it consumes the destroying resinous, oily, or other parts in from twelve to twenty-four hours. - (Engineers' club, [542 Philad.; meeting March 3.) Several facts are mentioned in support of the first form; and, as an experimental proof, the benzyl ether of nitrosoacetone was made and compared with the benzylnitrosoacetone obtained by the action of nitrous acid on benzylacetacetic ether. Since the isomerism of these bodies was established by differences in their physical and chemical properties, the first cannot contain a nitroso-group. Benzylnitrosoacetone from benzylacetacetic ether. CH, CO - C = N. OH - C7H7. Benzylnitrosoacetone from nitrosoacetone. Whether nitrosoacetone contains the group NH C=N-OH or the group 1 remains to be determined. The authors conclude that true nitrosobodies are probably produced by nitrous acid when it acts on the group CH; when acting upon the group = CH2, isonitroso-bodies containing the group - CN. OH result. (Berichte deutsch. chem. gesellsch., xv. 3067.) C. F. M. [544 GEOLOGY. Geology of the vicinity of Havana. - Pedro Salterain y Legarra has published a geological map which shows along the Cuban shore, in the jurisdiction of Havana and Guanabacoa, a narrow strip of modern rocks; then a band twice as wide, which he refers to the miocene. Next to this is a band of about the same width, colored as eocene. The rest is represented as cretaceous, with narrow tongues of eruptive rocks running through it in a general east and west direction, the largest of which begins at Regla. Guanabacoa is situated on it, and it extends eastward to the limit of the jurisdiction. To the south-west, along the Rio Marianao, the cretaceous becomes very narrow; and south of and including Pedroso, the eocene again appears. The first part of the accompanying memoir consists of a brief orographic and hydrographic description of the districts, together with a number of analyses of the water of the Rio Almendares and of various mineral-springs. Great difficulty was experienced, in studying the geology, from the heavy mantle of vegetable earth, and the consequent distance between outcrops. His classification of the formations is as follows: 1°. The quaternary or recent, containing the reef-formations of corals and zoophytes, detrital, and alluvial deposits. 2o. Post-pliocene, the relations of which to the quaternary or to the upper tertiary pliocene are uncertain. It generally consists of a sandy, whitish-yellow limestone, with many fossils generally identical with living species. In Matanzas a molar of a hippopotamus was found in a similar deposit. 3°. The miocene, which is placed between the overlying madreporic or quaternary and the eocene band. It extends along the northern slope of the first range of hills, and consists of a rock of generally identical character in all parts, a somewhat argillaceous white limestone, generally very fossiliferous, coarse, porous, and rough to the touch. Most of the fossils are casts. Zoophytes are abundant, as in the post-pliocene; but the relative proportion of mollusks, principally lamellibranchiates, is larger. Echinoderms are also of more frequent occurrence. 4°. The eocene, the most important formation in the island, which serves as a point of departure of comparisons between the formations. It lies at the base of the miocene, and rests uncomformably on the very inclined and dislocated beds of an older system, probably cretaceous. It contributes chiefly to the formation of the first range of hills parallel to the coast. The upper part consists of fossiliferous limestones dipping 10°-12° N. W.; and below are various beds of clay and limestone. A cephalopod (Aturia zigzag Sow.) occurs, with a large number of gasteropods, lamellibranchiates, some echinoderms and corals, and many Orbitoides Mantelli. 5o. The cretaceous, in which no fossils are found. It underlies the tertiary and overlies the western group of mountains, which some geologists have considered jurassic. The general strike of its beds is east and west, and their dip about 50° S. or S.S.E. In this formation occur the numerous deposits of asphalt, which appear to be contemporaneous with certain igneous eruptions, none of which have affected the tertiary. The eruptive rocks have been called 'Serpentinica formacion,' because serpentine is the prevailing rock in them. The characters of the rock are very variable. The serpentine is frequently associated with diallage, and yellowish-green olivine often abounds in the darker and more compact rock; there is also much oxide of iron and some oligist iron. The centre and highest part of the eruption is often occupied by diorite, then the olivine and diallage serpentine, and outside a talcose serpentine of brilliant lustre. Lists of the fossils found in the miocene and eocene are given with the localities in which they occur. M. Fernandez de Castro, in a lecture on the paleontological proofs that the island of Cuba was united to the American continent, says he believes that all the great geological divisions are represented in the island; but he adduces almost no evidence in support of this assertion. Those interested in the subject will find a bibliography of works relating to the geology of Cuba in vol. iii., p. 62.-(Bol. com. mapa geol. España, vii.) J. B. M. [545 METEOROLOGY. Spectrum of the aurora. - Professor S. Lemström, chief of the Finnish meteorologic observatory at Lodan Kylä (lat. 67° 24' N., long. 26° 36′ E.), has tried a novel experiment for determining practically the nature of the aurora. He placed a galvanic battery with conductors, covering an arc of 900 square metres (98 feet square), on the hill Oratunturi. He calls the arrangement a streaming apparatus. The conductors were constructed of uncovered copper wires, provided at each half-metre with fine erected points. The wire was led in slings to the top of the hill, and reposed on the usual telegraph-insulators. From one end of this wire a covered copper wire was conducted, on insulators, to the foot of the hill (600 feet high), and there joined a plate of zinc interred in the earth. In this circuit was put a galvanometer. Professor Lemström found the hilltop to be generally surrounded by a halo yellow-white in color, which faintly but perfectly yielded the auroral spectrum. This, he states, furnishes a direct proof of the electrical nature of the aurora, and opens a new field in the study of the physical condition of the earth. Further experiments in Enare, near Kultala, on the hill Pietarintunturi, confirm the above results. On Dec. 29, 1882, a straight beam of aurora was seen over the galvanic apparatus. - (Nature, Feb. 1.) H. A. H. [546 Meteorologic council of England. There will be published soon, by the English meteorologic council, Contributions to our knowledge of the meteorology of the arctic regions.' These will consist of observations, taken almost entirely by British ships, from 1819 to 1873. The council has also resolved upon obtaining data for synchronous weather-maps for the Atlantic Ocean for the thirteen months, August, 1882, to September, 1883, inclusive. [Charts for October, during the WestIndia hurricane season, would be an important addition.] The council publishes 78 per cent of its forecasts of wind and weather as verified. It has also instituted an investigation of the cause and character of London fogs, the best form of thermometer-screen, Stevenson's or Prof. Wild's metallic screen, the best manner of determining moisture in the air, and the motion of the upper air-currents. All these are still in progress. The latter experiments have been tried by firing six-pound shells with fuses of fourteen seconds. The vertical height reached before the explosion was 2,896m. (9,500 feet). The smoke cloud was clearly visible under a blue sky, and remained so for a considerable time. The council has made inspections of all the first and second class stations. A noteworthy fact has been brought out by the inspector of the stations in England: namely, that at some stations the abnormal deviations of the wind-direction from local causes is very great; e.g., at Shields, the vane points 220 to the right of the true direction for all except southwest winds. (Rep. meteor. council Royal soc., 1882.) [547 H. A. H. PHYSICAL GEOGRAPHY. The Gleisen valley, near Munich. A recent study, by Chr. Gruber, of this dry valley in the Bavarian plain, shows its connection with the period of glacial extension from the Alps, down the valley of the Isar, to the line of morainal hills, when the overflowstreams from the melting ice cut out channels now abandoned. (Ausland, 1883, 76, 87.) w. M. D. [548 Ice-caves. - Professor Fugger read an entertaining paper on ice-caves at the fourth international alpine congress at Salzburg last summer, in which he showed that the common idea of the summer growth and winter melting of the cave-ice is incorrect, although supported by high authority, as the elder Pictet, Murchison, Herschel, and others, and generally accepted in text-books. This error is doubtless based on the coolness of the caves in comparison with summer air, and their apparent warmth in the colder months, as well as on insufficient observations. Equally wrong is the view sometimes suggested, that the ice of caves survives from the glacial period. The grotto of La Baume, near Besançon, was known to contain ice in 1592; but in 1727 it was completely emptied by the duke of Lévi, to supply his army, encamped near by; yet in 1743 the bottom was covered again with ice, and a dozen ice-columns two metres high were formed. It is found by direct measure that the summer temperature of ice-caves is a little above freezing; but in winter it is several degrees below, the cold being derived from air that sinks in from the surface. Water trickles in at the temperature of the enclosing rocks, but is then soon frozen; and, if enough ice accumulates, it will last over the following summer season of melting. This is a simple and sufficient explanation. Summer evaporation has no effective share in producing cold, as the cavern air is very damp. Fifty-six ice-caves are known in the Alps, eight in the Jura and the Carpathians, four in middle Germany, and many more elsewhere. Notes from the north.-The Russian authorities have established meteorological stations at Mesen and Bereosoff in west Siberia. The international station at the mouth of the Lena reached its destination in August, and erected its dwelling on the island of Sagastir, with four observatories connected with it by covered pathways. -The Russian savant Eliséieff is pursuing ethnological studies in Russian Lapland, and reports that there are not in that area more than three hundred individuals of the Lapp race. The 'Louise,' after unsuccessful attempts to carry a cargo to the Yenisei in 1881 and 1882, finally returned to Europe with the muchhandled cargo, which had, part of the time, been stored at Hammerfest. For some time, at least, it is expected that the commerce of the Weser will flow preferably in any other direction than toward the Yenisei, if, indeed, these repeated failures do not put a quietus on trade by the Karagates. - The results of the hydrographic investigations carried on during the voyage of the schooner Willem Barentz' are exhibited in the December number of the Annalen der hydrographie for 1883, by Bogoslavski. - -The 'Jeannette' survivors left Liverpool for New York on the 18th instant. A chart of the north polar lands' by Berghaus, with special reference to the work of the international polar commission, is on the point of publication by Justus Perthes. The stations will be represented in red, and the limits will extend to latitude 60°. The waters eastward from the Taimyr peninsula have received the name of the Nordenskiöld Sea from the author of the map, which will, as a matter of course, represent the latest researches, and, moreover, will be sold for the inconsiderable sum of one dollar. The Danish expedition in Greenland is to be commanded by Lieut. Holm, who will give two years to the work. Dr. Boas proceeded to the German station at Cumberland Inlet, with the meteorological party, in order to make a special study of the Innuit. Poliakoff, who went in the summer of 1881 to the island of Sakhalin to make collections and explorations for the St. Petersburg academy of sciences, passed most of the winter on the south-east coast, at Taranka, Patience Bay. Rich collections, and a part of his report, with maps, have already been received, and will soon be published. He will now proceed to the western shore of the Gulf of Tartary, and continue his investigations between Sakhalin and Vladivostok. -An account of Dr. Stejneger's journey and observations in Kamtchatka and the Commander Islands of Bering Sea appears in Naturen, - a popular scientific monthly of Christiania, Norway. -W. H. D, 1550 (Europe.) Moors of Oldenburg. The construction of canals through the moorlands of the duchy of Oldenburg has given much accurate information about them, which is summarized by chief inspector T. Schacht. Their area is 1,000 km. (about 400 C miles) in a total surface of 5,376 km. The lower moors are perfectly level, and occupy depressions once filled with water. The upland moors are faintly undulating or slightly convex, sometimes climbing fifty feet above sea-level, and only occupy ground that has free drainage even at its lowest point. They begin at some moist locality with the growth of sphagnum, which, by its power of absorbing and holding moisture, spreads over the surrounding surface, and drives out the pre-existing vegetation. The thickness of these deposits sometimes reaches thirty feet. Great quantities of peat are taken from the moors, and hardly any other fuel is used in this region. It serves in brickyards, and even in iron and steel works; one establishment at Augustfehn requiring five to seven tons daily. The moors still in growth are impassable, but the older are of firmer surface. Of the latter, 270 km. are under cultivation, and a small part of the remainder is sometimes burnt over for growing buckwheat, filling the air with a dark, penetrating smoke. The moors are underlaid by sand or sometimes clay; and not unfrequently the remains of old forests of fir, birch, alder, hazelnut, and, on the higher ground, of oak, are found beneath the peat. Birch stumps are sometimes found growing on a thin layer of turf, showing an alternation of forest and moor conditions before the latter took final possession of the surface. Roman coins and weapons and the remains of plank roads are found four or more metres below the surface, implying a growth of that amount in two thousand years. Similar moorlands are common throughout northern Germany. (Peterm. mitth., 1883, 5.) W. M. D. [551 (Asia.) North-eastern Borneo and Sulu islands. — W. B. Pryer, British north Borneo company's resident at Elopura, furnishes a general description of this region and its tribes. One of the chief features of northeastern Borneo, or Sabah, is a low plain, some four thousand square miles in extent, enclosed by hills and mountains of sandstone and limestone on the north, west, and south. It has a heavy rainfall, and receives also the drainage of the high lands to the west in the form of numerous large rivers, along which there are many native villages in spite of the danger from fever. The higher land is thought probably suitable for European settlement. The forest fauna includes the elephant, rhinoceros, orang-outang, and some twenty kinds of monkeys, besides buffalo, deer, pigs, and bear, and many other animals. The largest orang-outang found measured four feet four inches in height; their appearance is deceptive, as they seem much taller. The adjoining islands of the Sulu archipelago are generally volcanic, though no volcanic rock is found on the part of Borneo visited. The islands are hilly, populous, generally cleared, and fairly well cultivated. They are surrounded by white coral strands, and, with their moderate temperature and pleasant, light breeze, are unusually attractive. The tribes of this region are very numerous. Some interesting details of their customs and condition are given. - (Proc. roy, geogr. soc., 1883, 90.) W. M. D. [552 (Pacific Ocean.) Mindanao. —The account of Dr. J. Montano's ethnographic exploration of this island of the Philippine group includes a few notes on its physical appearance. Its rocks are generally eruptive, partly covered with deposits of coral rock, implying a modern upheaval. Similar coral reefs fringe the shore. Near the northern end of the island is the circular Lake Mainit, about five miles in diameter, apparently situated in an ancient crater with steeply sloping borders. Earthquakes are frequent and violent in its vicinity. The surrounding mountains contain warm springs, and, especially when the atmospheric press |