The author further remarks that (C,EuH. €u)O and (C,AgH.Ag)O are analogous to the oxyd of Reiset's base, (NH,Pt)O, and that various facts lead him to believe that there are compounds analogous to the base (2NH,Pt)O, such as [(C1AgH)2Ag]O.

In a subsequent paper the author describes similar compounds containing gold and chromium, the constitution of which, however, is not yet clearly ascertained. Silver unites with allylene to form argentallyl, the chlorid of which has the formula [CH,Ag(CH,Ag2)]CI, so that the radical corresponds to the second series of acetylene compounds above mentioned. When metallic sodium is heated in acetylene the gas is readily absorbed and a compound is formed having the formula C ̧ÎNa, while the hydrogen set free unites with another portion of acetylene and forms ethylene, CH, and its hydruret, CH. Potassium acts in a similar manner but with more violence. At a higher temperature sodium replaces all the hydrogen and form C,Na2. The results given are to be considered as preliminary to a fuller investigation of the subjects.-Bulletin de la Société Chimique, March, 1866, pp. 176, 182.

W. G.

5. Isomerism.-BERTHELOT, in a memoir on a new kind of isomerism, proposes the following subdivision of this subject. Isomeric bodies-that is to say, bodies formed of the same elements united in the same proportions can be separated into a certain number of classes or general groups:

(1) Equivalent composition.-Substances which appear to have a purely accidental relation to each other; for instance, butyric acid C. H. O, and dialdehyde (C, H, O2)2.

8 8

4

(2.) Metamerism.-Bodies formed by the union of two distinct principles, so that in their formulæ a kind of compensation is established; for example, methylacetic ether, С2 H2 (С Í ̧O̟ ̧) and ethylformic ether, C, H, (C2 H2 04).

2

2

(3.) Polymerism.-Compounds arising from the union of several molecules to form one; this is shown in the case of amylene (C10 H10) and diamylene (C1, H10)2

10

(4.) Isomerism, properly so-called.-There are bodies that, differing in their properties, retain these distinctive features in their passage through certain compounds, the properties of which result from the internal structure of the compound molecule taken as a whole, rather than the diversity of the components which have produced it. This is observed in the cases of essence of terebenthine and citron, the sugars, the symmetrical tartaric acids, and the two classes of ethyl-sulphates.

(5.) Physical Isomerism.-By which is meant the different states of one and the same body, the diverse nature of which vanishes when the substance enters into combination. To these five classes, Berthelot proposes to append a new one, called kenomerism (from xevòv), distinct from all the others, though allied to metamerism.

(6.) Kenomerism.-Two different compounds may lose, by the effect of certain reagents which bring about decomposition, different groups of elements, and the remainders be identical in composition; these two de

rivatives, however, may yet be distinct the one from the other both in physical and chemical properties. They retain to some extent the structure of the compounds from which they take their origin. To take examples alcohol by losing 2 equivalents of hydrogen is turned into aldehyde : C1 HO2-H2 = C1 H1 02. Glycol, on the other hand, by giving up 2 equivalents of water, is converted into glycolic ether (oxyd of ethylene):

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4

Glycolic ether and aldehyde are isomeric; their composition is the same, but their properties, both physical and chemical, are extremely different. This is a good case of kenomerism. Again, essence of terebenthine combines with hydrochloric acid under different conditions to form two distinct hydrochlorates, the monohydrochlorate, C20 H16 H CI, and the dihydrochlorate, C2, H16 2H Cl. From the first body the crystalline compound C2, H16, camphene, is obtained, and from the latter C20 H16, terpilene, two hydrocarbons of very different properties.— Reader, July 7.

6. On a new determination of the velocity of sound in different media. -AUGUST KUNDT has, by a course of experimental investigations performed in the laboratory of Magnus of Berlin, arrived at new and very interesting results in regard to the longitudinal vibrations of gases, and disclosed a new method for the determination of the velocity of sound in gases and solids, which gives as accurate results as any other method, and besides is admirably adapted for the class-room.

After having enlarged our knowledge of longitudinal vibrations of glass tubes coated on the inside with lycopodium, Mr. Kundt closed one or both ends of the longitudinally vibrating glass tube; instead of the accumulations observed by Savart he found the lycopodium to form a beautiful regular wave-line with transverse ripplings, varying according to definite variations in the circumstances of the experiment.

Take a glass tube about four feet long and three-fourths of an inch in diameter, shake some lycopodium into the same so as to make it adhere like dust to the walls of the tube, close each end by a cork, hold the tube in the middle, and cause it to vibrate longitudinally; then there will always be 16 heaps of the lycopodium. The velocity of sound in glass being about 16 times as great as in the air, in the tube the distances between the heaps, produced by the stationary waves are corresponding parts of the wave-length of the tone in glass and air (here one-half wave-length). This number is therefore found to be independent of the dimensions of the glass-tube; Kundt has used tubes of from one foot long and one-twelfth of an inch diameter, to six feet long and three inches diameter. If the glass tubes vibrate with two nodes, there are always 32 heaps; with three nodes there are 48 heaps,-the distance between the heaps being always one-half wave-length for air; but the glass tubes when held in the middle give one-half wave-lengths, that is, when vibrating with two nodes one wave in glass, when with three nodes waves in glass, thus giving :16=1:32:48.

When the tube is held in the same manner, that is, when its length is the same part of a glass-wave, the distance of the heaps (half-wave lengths in the gas) will be proportional to the velocity of sound in the gas, or the number of heaps will be inversely proportional to that velocity.

For tubes filled respectively with air, carbonic acid, illuminating gas and hydrogen, Mr. Kundt obtained respectively 32, 40, 20, and 9 heaps, from which the velocity of sound (air =1) is for carbonic acid 33=8, illuminating gas 16, hydrogen 323.56. Dulong found, by a very difficult method, for carbonic acid 79, for hydrogen 3.8

To obtain still greater accuracy, and also determine the velocity of sound in different solids, Kundt closes one end of the glass tube by a cork, movable by means of a wire; while the other end is closed by a perforated cork, enclosing a rod of the solid submitted to the experiment. This solid rod has one-half of its length in the glass tube, which itself is somewhat longer than the entire rod. This rod is set in vibration.

It will easily be seen, that for the same mode of vibration the velocity of sound in the solid will be directly proportional to the length of the rod, and inversely proportional to the distance of the lycopodium heaps in the glass tube.

With a brass rod 941.5 mm. long and 5 mm. diameter, Mr. Kundt obtained, in three different experiments, in each making numerous measurements of the distances, the velocities 10.87, 10.87, 10.86. Another brass rod gave 10.94 and 10.90. Similarly for steel, 15.345, 15.334 and 15.343; for glass, 15.24, 15.25 and 15.24; for copper, 11.960.

Wertheim found for cast-steel, 14.961; for steel wire, 15,108; for copper, 11.167.

The above leaves no doubt that Mr. Kundt has enriched science with a new method for the determination of the velocity of sound in solids, gases and vapors, alike excellent for a high degree of accuracy in its numerical determinations, ease of execution, elegance and simplicity, making it exceedingly convenient for lecture experiments.

We are engaged in experiments to try the application of this method to liquids. Poggendorff's Annalen, 1866, cxxvii, 497-523; l'Institut, 1866, p. 15-16; Cosmos, 1866, iii, 98–100.

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G. H.

7. The vapor of water not absorbent of much radiant heat.-TYNDALL and FRANKLAND have, on the basis of some experiments, ascribed to watery vapor an excessive absorptive power for heat. The former even says: Comparing a single molecule of aqueous vapor with an atom of ether of the main constituent of our atmosphere, I am not prepared to say how many thousand times the action of the former exceeds that of the latter." (Lecture on Radiation, Sect. 12.)

Magnus has objected to these experiments because they did not insure the absence of condensed vapors; he has now succeeded in constructing an apparatus which affords positive proof of the presence or absence of condensed vapor, "fog." He has found that the radiation (which is proportional to the absorption) of the following gases and vapors gave the following deflections with his very delicate thermo-multiplier, all the gases being heated about to 230° C.: dry atmospheric air 3 mm.; air having passed through water 3 to 5; dry carbonic acid gas 100 to 120; common illuminating gas, about the same; air having passed through boiling water, irregular, but maximum deflection only 20, and only gradually increasing to this amount, while carbonic acid and illuminating gas produced the deflection suddenly. When the water boiled so strongly that fog became visible at the radiating point, the deflection was above 100.

From the circumstances attending the deflection of 20 mm., even this may be ascribed to the presence of fog.

Magnus, as well as Dove, Quincke, Riess, Kundt, and others who witnessed the experiments, have seen that air passed through water at the common temperature never gave a greater deflection than 3 mm.; when saturated at a higher temperature never greater than 20 mm.; and only when fogs appeared the deflection became about as great as with carbonic acid gas, viz., 100 mm.

Magnus also experimented with a number of other vapors. He also shows how the phenomena of dew are in accordance with his view; that dew would be impossible if watery vapor had so great an absorptive power as Tyndall supposes; but that all the deductions of Tyndall and Frankland in regard to climate and the glacial period remain true if we substitute fog or foggy vapor for true uncondensed vapor; and finally, that the aqueous absorption lines in the spectrum observed by Cooke and Secchi are contradictory to any extraordinary absorptive power in actual vapor.-Poggendorff's Annalen, 1866, cxxvii, 613-624.

G. H.

8. Solar spots influenced by solar refraction-In a certain sense the observations of Carrington (this Journal, xxxviii, 142) and of Spörer have thrown the subject of the physical constitution of the sun back into uncertainty and doubt. But it seems that as little as Kirchhoff's observations upset our views of the constitution of the Laterna mundi of Copernicus, so also the remarkable observations above referred to seem rather destined to confirm than to destroy the more ancient hypothesis of several atmospheres of the sun; for Mr. Dauge, of the Academy of Brussels, has shown how all the striking phenomena observed by Carrington and Spörer may be fully accounted for by the refraction of the emergent rays in the atmosphere exterior to the photosphere of the sun. By a very simple elementary process Mr. Dauge demonstrates that such an atmosphere by its refraction will produce the following effects: 1st, augment the apparent diameter of the sun; 2d, augment the mean period of rotation of the sun; 3d, retard the apparent motion of a spot in proportion as the same recedes from the center toward the rim of the sun; 4th, the apparent period of revolution of a spot increases with its solar latitude; 5th, the solar refraction produces an apparent motion of the spots in latitude (the latitude decreasing from the eastern rim to the middle, and increasing from the middle to the western limb of the sun). Taking the horizontal refraction of the exterior atmosphere less the apparent diameter of the sun at 25°, and neglecting some insignificant terms, Mr. Dauge obtains the following value of the period of revolution of a spot at a solar latitude

days 90° +8 25.30X 115°

Taking the mean of Carrington's observations for every fifth degree of latitude, Dauge gives the following comparison between the observed (0) and calculated (C) values of the period of revolution expressed in days:

10° 15° 20° 25.11 25.20 25.51 25.73

C 25.30 25.33 25.38 25.50 25.68 25.92 26.22 26.80 28.33 Toward 45° the observations are very scarce, hence of little weight.

The agreement of these numbers is sufficient to prove that this refrac tion is the principal cause of the phenomena observed by Carrington and Spörer. It may be well to remember that Secchi had suggested the influence of solar refraction some time before the publication of Dauge's work.-L'Institut, 1866, pp. 159, 165–168.

T

II. MINERALOGY AND GEOLOGY.

G. H.

1. Geological explorations in Northern Mexico; by A. RÉMOND. Compiled from his notes, and prepared for publication, by J. D. WHITNEY. 18 pp. 8vo. San Francisco, 1866.-We cite a few paragraphs from this valuable report on the geology of Northern Mexico.

"The mountainous region comprising the central and western portion of Northern Mexico belongs to the four states of Durango, Chihuahua, Sinaloa, and Sonora. Considering how celebrated this portion of Mexico has become for its mines and metalliferous veins, and how much has been written about it, it is surprising how little exact information has hitherto been obtained with regard to either its geography or geology. On comparing the principal published maps of the region in question, it will be seen at once how much they differ from each other in their delineations of even its main topographical features, while the details are entirely wanting.

"The name of the 'Sierra Madre' is usually applied to the main range of mountains of this country, or the western border of the plateau which stretches north through the territories of the United States, forming what may be called the great orographical feature of the continent. In northwestern Mexico this crumpled border of the great plateau comprises an extensive mountainous region, by no means forming a continuous single chain, but rather several central ranges, with associated groups of parallel ridges, all having the same general course, which is approximately northnorthwest, and south-southeast. As the breadth of the chain widens as we go toward the north, so, too, that of the valleys increases in that direction, the whole system of mountains and valleys spreading out in something like a fan shape.

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"Going north, the chain appears to sink gradually, although determinations of altitude in northern Mexico are extremely few in number. It is certain that there is, in about latitude 32°, a depression of the mountain ranges which extends entirely across the continent, and which would enable the traveler to cross from the Atlantic to the Pacific, without necessarily surmounting any elevation greater than four thousand feet.' The southeastern range is the highest, and the culminating point is said to be the Cerro de Cuiteco, sixty leagues northeast of Jesus Maria, on the western border of Chihuahua. The approximate altitude of the Cumbre de Basascachic is 7429 feet, and that of Guadalupe y Calvo, 7825 feet. 1 See Emory, in Mexican Boundary Report, vol. i, p. 41. AM. JOUR. SCI.-SECOND SERIES, VOL. XLII, No. 125.-SEPT., 1866.