The formation of this salt, together with the lead salt, shows that from this acid both monobasic and dibasic salts can be formed.

12 7

The formula of the acid is C,H,,O, and in the oxidation of the glycogen we can assume that the following reactions take place: CH,,O,+H2O+2Br=C,H,,O,Br,. Adding silver oxide to the bromine compound we have:

C.H,,O,Br,+Ag2O=C ̧¤‚‚0,+2AgBr.

6

From analogy, it would seem proper to apply to this acid the name glycogen acid.

The preceding analyses and reactions show conclusively that by the action of bromine, water and silver oxide on glycogen, an acid is formed which bears the same relation to glycogen as "dextronsäure" to dextrin. On comparing this acid with the descriptions of "gluconsäure" and "dextronsäure," we see that the glycogen acid differs from the two no more than the two differ from each other. There is also the same relationship existing between glycogen acid and the acid or acids obtained by the oxidation of amylum and paramylumt by Haberman, which latter show but few points of difference from "gluconsäure" and "dextronsäure."

February 26th, 1876.

ART. LII.-On the existence or not of Horns in the Dinocerata ; by RICHARD OWEN. (Letter to the Editors of this Journal, dated London, Feb. 24, 1876.)

GENTLEMEN: Among the new forms of extinct Eocene mammals of America, for which science is indebted to Professor O. C. Marsh, those which he refers to "the new order Dinocerata" are the most singular.

The study of their characters, especially as described and illustrated in your Journal,§ has led me to submit a few remarks on the subject of "horns." These weapons in mammals, if formed or supported by bone, are either "autogenous" or "exogenous," either "epiphyses" or "apophyses;" terms which signify, in a word, either, that the horn is ossified from an independent center and

* Annalen der Ch. u. Pharm., clv, 120. Ibid., clxii, 297. Ibid., clxxii, 11. § Vol. xi, February, 1876, p. 163.

afterwards coalesces with a cranial bone, or that it grows, as a process, from a cranial bone.

The giraffe yields an instance of the "autogenous" horn, and its skull, in either the recent or fossil state, shows the basal sutures. In other species the horns or horn-cores are "exogenous;" and such, in the absence of the sutural evidence, are the parts called "horn-cores" in the Dinocerata.

But before elevations or processes of cranial bones can be pronounced to be "horn-cores," the evidence of the horns they supported should be forthcoming. Paleontology, it is true, infers the existence of horns supported on bony bases, or "horn-cores," in extinct species in which such horns have perished. Bos antiquus, Bison priscus, Sivatherium, Bramatherium, are rightly referred to the "hollow-horned" group, and the two latter may seem more germain to the present question, seeing that the "horn-cores" are in two pairs. Such conclusion is based on the presence of foramina and ramified grooves upon the surface of the " cores,' " which are known to be the effects of the penetration and pressure of bloodvessels supplying the growth and renovation of the horny sheaths of such bony processes. The same evidence reveals the true nature of the horn-cores, which may be covered with skin instead of horn, such as are the horns of deer, from which when complete the skin is shed.

In the absence of such evidence the paleontologist infers that smooth unfurrowed protuberances or processes of cranial bones were covered, like the rest of the outer surface of the bones developing them, with persistent periosteum and skin, in the existing animal. He refrains from calling them "horn-cores," and from defining the extinct species mauifesting them, as " horned," "fourhorned," or "six-horned," Dicerata, Tetracerata, Hexacerata; or, as in the case of the hornless herbivores of the Wyoming Eocene, Dinocerata: because such terms imply the possession by those extinct quadrupeds of weapons of which there has not, at present, been given any evidence.

Professor Marsh, indeed, candidly admits in regard to the protuberances which suggested the generic name Dinoceras, that they "may possibly have been covered with thick skin and not with true horn." But we have no evidence of the integument having been thicker, or other on the protuberances than on the cranial bones developing them.

It may be noted that the hornless exceptions in the group of existing herbivorous quadrupeds with true horn-cores and horns, the hornless Moschida, e. g., are furnished with other weapons of defense, a pair, namely, of long, edged, and sharp-pointed canines descending from the upper jaw.

The hornless Dinoceras was similarly armed, and Professor Marsh believes he has evidence of a sexual difference of size in those dental weapons, which would yield another analogy to the existing Musk-deer. But the dental and osteal characters of the + Loc. cit., p. 164.

pentadactyle Dinoceras are consistently "perissodactyle." The truly remarkable peculiarity of its skull is the tendency of the outer wall of the bones to extend into ridges and bosses; and this not only in the cranium proper and upper jaw, but also in the lower jaw. If these bosses were legitimately interpretable as "horn-cores," we must give the animal a pair of horns descending from the under and forepart of the mandible to match the pair ascending from the maxilla. But the singular processes descending and diverging, as a pair, from the mandibular rami, show as marked an absence of any indication of their having been sheathed with horn as do the pairs of protuberances from the nasal, maxillary, and the frontal bones above.

SCIENTIFIC INTELLIGENCE.

I. CHEMISTRY AND PHYSICS.

1. Diplometer.--M. LANDOLF has invented an instrument for measuring the diameter of objects without touching them and independently of their movements. A wedge-shaped piece of glass is cut in two along a plane perpendicular to the edge of the wedge, and joined together again after turning one piece 180°. Looking through the line of junction of the prisms, objects will appear double, because the prisms will deviate the rays in opposite directions. When the two images appear just in contact the doubling will be just equal to the diameter of the object. Hence knowing the distance we can compute the diameter, or vice versa. The prisms slide over a graduated rod so that the object being placed at one end they are moved until the two images are just in contact, when the distance furnishes a ready means of determining the diameter. In the instrument actually constructed a distance of 42 mms. corresponded to an overlapping of 1 mm. Consequently tenths of a millimeter were readily measured. Evidently motions of the object do not affect the measure since both images move together.-Comptes Rendus, lxxxii, 424.

[Numerous applications of this instrument will suggest themselves. In natural history the dimensions of various parts of animals or plants, whether large or small may be found, and in physics objects which cannot be touched, as bubbles, vibrating bodies, &c., may be quickly measured. By setting the prisms as an eye-glass this instrument would form a convenient substitute for a telescope, in measuring distances with a telemeter.]

F. C. P.

2. Specific Heat of Gases.-M. WIEDEMANN has published in full his measurements of the specific heat of gases referred to in a recent number of this Journal (cviii, 465). His results are given in the following table in which the first column gives the name of the gas, and the second, third and fourth its specific heat under constant pressure at temperatures of 0°, 100° and 200°. The last

-Pogg. Ann., clvii, 1.

3. Crooke's Radiometer.-Mr. G. J. STONEY presents an explanation of the apparent repulsion produced by heat, according to the Kinetic theory of gases. Mr. Crookes has shown that the pressure produced on a blackened surface of two square inches by the light of a standard candle six inches distant would be 001772 grains or somewhat less than 01 milligram per square centimeter. Assuming that the pressure of the air in the interior is reduced to 1 mm. there would still be something like a hundred million of millions of atoms in each cubic millimeter. These atoms will consist in part of oxygen and nitrogen from the air, of mercury and hydrocarbons, and probably in part of platinum, glass and other substances in a gaseous form.

The blackened surface will be heated by the candle more than the glass by an amount which may be assumed at 1° and the air in contact with it will vary in temperature from that of the disk to that of the enclosing air. Were the air at its ordinary pressure the heated layer would be very thin, and may be estimated at about 0005 mm., or about the wave-length of green light. With the small pressure here employed, however, the case is quite different, and the thickness of the layer would equal 0005 X (7600)1-33, or over a decimeter. The heated layer therefore extends to the wall of the surrounding vessel, and now a heat engine is formed by the particles of air which strike the disk with a velocity due to a temperature of perhaps 15°, and are repelled from it with a velocity due to its temperature of 15.1°. The resultant pressure on the disk may be readily computed and is found to be 0115 milligram which agrees closely with 01, as observed by Mr. Crookes. In other words a difference of temperature of 1° C. is sufficient to account for the observed pressure.-Phil. Mag., 1, 177.

[The measurement here referred to, is described in Engineering, Feb. 18th, and was effected in the following manner: A torsion balance was constructed with a horizontal glass fiber and with a horizontal arm terminating in a cup at one end and in a disk of pith at the other. A small piece of iron weighing a hundredth of a grain was raised by a magnet and dropped into the cup. It was then found that the fiber must be turned through 100021° to bring the arm back to its original position. The light of a candle at a distance of 6 inches was next allowed to fall on the pith, when a torsion of 1775° was required to bring it back. This corres

ponds to 001772 grains, or about an eighth of a grain per square foot. From this it would appear that the light of the sun would be equivalent to 32 grains per square foot or 57 tons per square mile. Mr. Crookes further applies this instrument as a photometer and suggests its application to observatories to determine the total amount of sunlight received during the year. The number of revolutions could be counted by attaching a magnet to the radiometer which should act on a magnetic needle moving a counter outside of the glass case. Similarly the power of the instrument might be transmitted through the glass without the usual loss by friction.

Numerous other articles appear on the same subject. Poggendorff and Neesen (Bibl. Univ., ccxvii, 84, and Phil. Mag., 1, 251) publish independent series of experiments from which they conclude that the repulsion is due to convection currents. Several articles appear also in Nature,' on the radiometer; on p. 391, Mr. Crookes shows that the repulsion is inversely as the square of the distance and compares the effect of rays of various wave lengths. On page 324, Mr. Hutchinson states that a radiometer with mica vanes on metallic supports revolves more rapidly with dark heat than with light, but Mr. Crookes replies that pith should be used as the absorbing substance, since metals give erratic results.] E. c. p.

C.

4. The Gram Magneto-electric machine.-M. TRESCA has made a careful measurement of the power required to drive a large and a small gram machine and compared the result with the light generated. A photometer disk was used, of which one portion was illuminated only by the electric light and an adjacent portion only by a carcel burner consuming 40 grams of oil per hour. Much trouble was experienced from the difference in color of the two lights, and the equality was best obtained by interposing two plates of glass, one of light green and the other of light pink. Owing to irregularities in the carbons the light continually underwent irregularities sensible only to the photometer. The light of the larger machine was placed 40 meters from the disk and the burner moved until the square of their distance should be as 1850:1, which was about the mean ratio of the two lights. When the two portions of the disk appeared equally bright the observer gave a signal and instantly the power and velocity were observed. The larger machine had a length of 80 cms., width 55 cms., and height 58.5 cms. The average number of turns per minute was 1274, and the work 576 kilogrammeters or 768 horse-power. The light being 1850 burners, would equal 415 of a horse-power per 100 burners, or 31 kgms. per burner.

The smaller machine had a length of 65 cms., breadth of 41 cms., and height of 50.6 cms. It made 872 turns per minute, and gave a light of 302-4 burners. This required 211 kgms., or 2-8 horse power, equivalent to 92 of a horse power per hundred burners, or 69 kgms. per burner.

The consumption of oil to produce a light equal to that of the larger machine would be about 71 kgs. per hour or 194 cubic

AM. JOUR. SCI.-THIRD SERIES, VOL. XI, No. 65.-MAY, 1876.