1837, p. 61, 62 and 152); but calls the mineral from the West Hartford trap, anthracite. He remarks that the coaly substance from "the trap at Farmington, Southbury and Rocky Hill, Hartford, ignites slowly and burns without odor; further that the same from the shale at Berlin, and the bituminous shales of Southbury, is " compact bitumen "; that "in many instances when freshly taken from the quarry it is semi-fluid, or only so much inspissated as to form what is called elastic bitumen or mineral caoutchouc, and burns with a white flame and much smoke."

Percival recognized the igneous origin of the trap, and the fact that the Triassic or "Secondary formations were formed from the debris of the Primary rocks." The remark with which he closes the subject implies that he supposed the bituminous material to have come from the same deep-seated source as the trap. Yet his facts, and his special presentation of them, are so well calculated to prove that the bituminous shale and limestone are the sources of this "indurated bitumen," and that the trap, while on its way to the surface, took in the gaseous hydrocarbon distilled from the rocks by the heat-nearly at the same time that it took in moisture in vapor from some sources of water and so became hydrated and vesicular-(a view I have for some years held*), that it is reasonable to suspect that Percival may have entertained this opinion although it was not his final conclusion. It seems hardly probable that, after observing with so much detail the wide distribution of the bituminous shales and limestone, he should have attributed all the impregnating hydrocarbon of these rocks to the igneous eruptions.

The view that the bituminous material in the trap came from the shales and limestone and was taken in by the hot trap on its way through these rocks, is brought out by Mr. G. W. Hawes in this Journal, on page 56 of volume ix, 1875.

J. D. D.

SCIENTIFIC INTELLIGENCE.

I. CHEMISTRY AND PHYSICS.

1. Underground Temperatures.-The subject of underground temperature is daily receiving more attention. Sir William Thomson, in the Phil. Mag. for May, 1878, No. 32, page 370, proposes the following problems for solution:

Problem I. A fire is lighted on a small portion of an uninterrupted plane boundary of a mass of rock, of the precise quality of that of Calton Hill, and after burning for a certain time is removed, the whole plane area of rock being then freely exposed to

*This water I have supposed to have largely underlaid the Triassic formation, occupying spaces between it and the subjacent metamorphic rocks, and also to have existed in and among the strata of the formation-the beds being often porous sandstones and loosely united (this Journal, vi, 1873, page 108); and if mainly from beneath the Triassic, it would have been taken in just before the hydrocarbon vapors.

the atmosphere. It is required to determine the consequent conduction of heat through the interior.

Problem II. It is required to trace the effect of an unusually hot day on the internal temperature of such a mass of rock.

Problem III. It is required to trace the secular effect consequent on a sudden alteration of mean temperature.

Problem IV. It is required to determine the change of temperature within a ball of the rock, consequent upon suddenly removing it from a fluid of one constant temperature and plunging it into a fluid maintained at another constant temperature.

Thomson confines himself mainly to the mathematical discussion of problem I, since the solution for problem I can be applied with slight variations to problem II and III, and problem IV is an example of Fourier's well known solution for a globe, which has lately been treated in detail by Professors Ayrton and Perry.

Problem I is thus stated according to the author's assumptions: "An infinitely small area of an infinite plane, terminating on one side a mass of uniform trap rock, which extends up indefinitely in all directions on the other side, is infinitely heated for an infinitely short time, and the whole surface is instantly and forever after maintained at a constant temperature. It is required to determine the consequent internal variations of temperature."

From the mathematical expression obtained from this statement the following conclusions result.

(1) The simultaneous temperatures at different points equidistant from the position of the fire are simply proportional to the distances of these points from the plane surfaces.

(2) The law of variation of temperature with distance in any one line from the place where the fire was applied, is the same at all times.

(3) The law of variation of temperature with time is the same at all points of the solid.

(4) Corresponding distances in the law of variation with distance increase in proportion to the square root of the time from the application and removal of the fire; and therefore, of course, corresponding times in the law of variation with time are proportional to the squares of the distances.

(5) The maximum value of the temperature, in the law of variation with distance, diminishes inversely as the square of the increasing time.

(6) The maximum value of the temperature in the law of variation with time, at any one point of the rock, is inversely as the fourth power of the distance from the place where the fire was applied.

(7) At any one time subsequent to the application of the fire, the temperature increases in any one direction from the place where the fire was applied to a maximum at a distance equal to

2kt, and beyond that falls to zero at an infinite distance in every direction. The value of k for the trap rock of Calton Hill AM. JOUR. SCI.-Third Series, VOL. XVI, No. 92.—August, 1878.

being 141, when a year is taken as the unit of time, and a British foot the unit of space, the radius of the hemispherical surface of maximum temperature is therefore 16.8Xt feet. Thus at the end of one year it is 16.8 feet, at the end of 10,000 years it is 1689 feet, from the origin.

(8) At any point at a finite distance within the solid (which, by hypothesis, is at temperature zero at the instant when the fire is applied and removed), the temperature increases to a maximum at a certain time, and then diminishes to zero again after an infinite time; the ultimate law of diminution being inversely as the square root of the fifth power of the time. The time when the maximum temperature is acquired at a distance r from the place where the fire was applied, is 10%, or, according to the value

t2 237.5

t2

found for trap rock, of a year. Thus it appears that at one. French foot from the place of the fire, the maximum temperature is acquired a day and a half (more exactly 154 days) after the application and removal of the fire. At 154 French feet from the fire, the maximum temperature is reached just a year from the beginning, and at 1540 feet the maximum is reached in 10,000 years.

Many observations on underground temperatures have been made by Dr. Schwartz in the mining district of Schemnitz in Hungary. A resumé of his work has appeared in Nature, April 11, 1878. Observations were taken by the means of mercurial thermometers, placed in holes 422 and 79 of a metre, which were bored in the rock of thirty-eight galleries. In the final reductions Dr. Schwartz compares the temperature in the deepest galleries of each shaft with the assumed mean annual temperature of the ground at the shaft mouth. He also gives his reasons for believ ing that the mean temperature one meter deep in the localities in question is 1° C. higher than the mean temperature of the air. From the reduced observations we learn that there was a total increase of 38°.3 C. in 1587 m., which is at the rate of 1° C. in 414 m., or 1° F. in 75.5 feet.

The comparison of the deepest observations with the shallowest which was undertaken as a check upon the above, gave a mean of 1° F. in 725 feet.

The rock consisted mainly of trachyte and greenstone. From an analysis of the rocks the report appears to indicate important variations in temperature, due to the decomposition of metallic sulphides. Observations have also been taken by the manager of the Boldon Colliery, between Newcastle and Sunderland, in holes bored upward to a distance of ten feet from some of the deepest seams. The thermometer used is characterized as a slow action one-not a self-registering one-and was placed in the bottom of the hole and protected by an air-tight plug. The distance of the thermometer from the surface of the earth was 1365 feet.

This thermometer, thus placed, gave an indication, April 26, of 75°, which was the same for four consecutive weeks. The same thermometer was placed in the same manner in another hole, 1514 feet from the surface of the earth. Observations taken in July and August gave a temperature of 79°. The mean annual temperature at the surface was assumed to be 48°. For the interval of 149 feet between the holes, there was an increase of 4° F. which is at the rate of 1° F. in 37 feet. In the whole depth of 1514 feet from the lower surface to the lower hole we have an increase of 31°, which is at the rate of 1° F. in 49 feet. Late observations in India indicate that the Summer heat influences observations taken even at a depth of sixty feet.

J. T.

2. On the Law of Solid Volumes.-SCHRÖDER has investigated the question of the volume occupied by elements in the solid state in compounds and has discovered a law which he calls the law of solid volumes and which he enunciates as follows: In every solid compound, the volume in the solid state, i. e., the stere, of one of its elements determines, by means of the forces active during crystallization, the assumption, by all the other elements, of the same solid volume or stere. In other words, one of the elements assimilates to itself all the others. The molecular volume of a compound in the solid state requires as many atoms as is necessary to make the volume of each element an entire multiple of the controlling stere. A solid molecule contains therefore only entire steres of each element contained in it. The solid molecule of zinc contains Zn, and of zinc oxide Zn303, because, both alone and in the oxide three zinc atoms occupy the volume of five steres, the three oxygen atoms occupying the volume of three. In a formula, Schröder indicates the number of steres of an element by an ordinary, and the number of atoms by a sub exponent. A stere-value is marked by a line over it and a volume calculated or observed, by a line beneath it. Thus silver for example, Agi=2X5·14-10-28; obs. vol. 10-28, means that an atom of silver or 108 grams takes a space of 10.28 cubic centimeters; i. e., twice 5'14 c. c., or two silver steres. For the chloride, iodide and bromide of silver, he gives Ag2Cl2=5X5·14= 25.70; obs. vol. 25·7. Agi Br6 X 514-30-84, the obs. vol. Ag?16=8X5·14 41°12, also the obs. vol. In all three, the controlling volume is the silver stere, silver entering as two steres, chlorine as three, bromine as four and iodine as six. The author has applied his law to a large number of chemical compounds and obtains some significant results.—Ber. Berl. Chem. Ges., xi, 1109, May, 1878.

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G. F. B.

3. On Flame Temperatures.-ROSETTI has continued his experiments upon the temperatures of flames and finds that although gas flames are much increased in volume by pressure, the corresponding zones show nearly the same temperatures, the difference being only 20° for a great variation of pressure. The maximum

temperature in a powerful Bunsen burner consuming to one volume of gas 2.2 of air, was 1360°; becoming 1150° when the volumes of gas and air are equal. Using a Bunsen burner closed below, the maximum temperature observed with a mixture of gas and nitrogen was 1240°, when the proportions were 1 of gas to 1 of N, and with carbon dioxide, 1190°, the proportions being as 1 to. A stearin candle flame had a temperature of 940°, a Locatelli lamp of 920°, a petroleum lamp without a chimney 920°, in the luminous and 780 in the smoky portion, with a chimney 1030°, an alcohol lamp 1170° with alcohol of 912 sp. gr. and 1180° with alcohol of 0.822. Hence the correctness of diluting alcohol for burning.-Ber. Berl. Chem. Ges., xi, 809, April, 1878.

G. F. B.

4. On the Production of Ozone, Hydrogen peroxide and Persulphuric acid by Electrolysis.-The inferior volume of oxygen gas set free in the electrolysis of water acidulated with sulphuric acid, at first observed by Faraday, has been noticed by all physicists who have used the voltameter. BERTHELOT has undertaken to measure this loss and to determine its cause. That it is not due to the production of hydrogen dioxide by the electrolytic ozone acting on the water, is shown by the fact that water and ozone do not combine together directly. Nor does the hypothesis that the oxygen splits into ozone and antozone during electrolysis fit the case, since the relation of the active oxygen existing as gas is to that existing in the liquid, so small, only a twentieth part. In one of Berthelot's experiments, there was 2.2 mgrms. active oxygen in the gas collected and 44 mgrms. in the liquid. Moreover, Meidinger has shown that when the sulphuric acid used had a density of 14, the amount of oxygen collected may fall to two-thirds of its theoretical value. In Berthelot's experiment, 12.2 c. c. hydrogen was collected in ten minutes, but only 3.6 c. c. of oxygen instead of 6:14. Since the oxidizing body found in the solution occurs only when this is acidulated with sulphuric acid, Berthelot concludes that it is really persulphuric acid; a view which its reactions confirm. Further, oxygen is gradually disengaged from the liquid, reaching in the course of a few hours, the theoretical quantity and even surpassing it. The bearing of these facts upon the use of sulphuric acid in a voltameter, is evident.-Bull. Soc. Ch., II, xxix, 348, Apr. 1878.

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G. F. B.

5. On the Polyiodides.-JOHNSON, who in 1876 discovered potassium triiodide, ordinarily represented as KI,, has experimented to ascertain whether the more probable formula is not KI, analogous to HgI, and whether one of the potassium atoms cannot be replaced by a univalent metal, or two atoms in two molecules KI12 by a bivalent one. Silver iodide, potassium iodide and free iodine were dissolved in the proportion to form AgK,I,2. On slow evaporation, potassium silver iodide first separated in crystals, next crystals of potassium triiodide and lastly crystals having the formula AgKI, KI. On repeating the preparation, using the proportions of this formula, only these

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