Imágenes de páginas
PDF
EPUB

materials, could only yield about 30,000 metre-kilogrammes of force.

Now the daily work of the heart alone is estimated by Donders at 86,000 metre-kilogrammes, and it is an extreme ander-statement to assert that the total daily work of the body in health is 100,000 metre-kilogrammes. To do even this quantity of work, twice the quantity, or 200,000 metre-kilogrammes of force must, as Heidenhain has proved, be provided; so that even taking the highest possible calculation of the quantity of oxygen which could pass into the tissues, we see that it cannot account for one-sixth of the work done in them. It is more probable, indeed, that it cannot account for one-sixtieth. To supply the minimum force per diem exerted in the body, there must be a daily exudation of about 264 litres, or 1-ton, if the exudate contains as much oxygen as

arterial corpuscles; or, 3500 litres, or 37-tons, on the more probable supposition that

it will not dissolve more than water will.

These figures appears to me to furnish a complete answer to the current theory of tissue-oxidation, and to force us inevitably to the conclusion so clearly pointed out by Mayer, namely, that the whole, or nearly the whole, of the animal oxidation, is effected in the blood itself, and consequently that there must exist some provision by which chemical force set free inside a capillary is converted into mechanical work in the tissues outside of it.

This view of the nature of animal oxidation tends to define more clearly our knowledge of the functions of the blood. Nutrition is one of its functions. It carries with it in its course the appropriate pabulum for the repair of all the tissues of the body. Bones, nerves, glands, and muscles, all alike reproduce their elementary parts at the expense of material derived from its fertilizing stream. And as these elementary parts attain their term of life they decompose and liquefy, passing again into the blood, for the most part through the same lymphatic vessels which take back the excess of the nutritive fluid. In the lymphatic vessels and glands much of the lymph is once more organized into blood, but the products of the disintegration of tissue are probably incapable of this renewal, and, in the absence of evidence must be supposed to return into the blood in an unorganized condition.

Equally important with the foregoing is the function of oxidation, to which the force as well as the heat of the body is due. Nitrogenous as well as non-nitrogenous bodies are oxidized in the blood, and though we do not yet know the precise conditions or the precise mode in which the oxidation

is effected, we are justified in inferring that it is by the direct agency of the corpuscles. There is on this view no ground for the assumption that either force or heat is due exclusively to the oxidation of one or the other class of organic compounds. Both are oxidized, and one is as likely as the other to be the motive power. Even the muscle itself, inasmuch as it is finally oxidized in the blood, may give rise to muscular work, and we must therefore conclude that Traube's hypothesis is as much an over-statement on the one side as Liebig's was on the other.

The changes effected by the blood in the exercise of its functions are subject, to a most remarkable extent, to the control of the nerves; and little as we know of this the most obscure region of physiology, we cannot avoid the conclusion that they are directly concerned in the transformation of chemical force into mechanical effect. The muscular currents of electricity, which have been so carefully studied by Du BoisReymond, Helmholtz, Heidenhain, and many others, are, no doubt, closely connected with this conversion; but I will abstain from speculations which are apt to degenerate into bare guesses. Dim foreshadowings of great discoveries lie before us, and it is better, after clearly stating to ourselves the truths already established, or made probable, to wait with humility, watching till diligent and patient search shall have been rewarded with fresh unveilings. If we can clear a .point or two in the intricate forest of knowledge which lies before us, we shall have done truer work than by any amount of speculation.

[ocr errors]
[ocr errors]

THE LUNAR CLEFTS–MARE VAPORUM-JUPITER'S

SATELLITES-OCCULTATIONS.

BY THE REV. T. W. WEBB, A.M., F.R.A.S.

In our last paper we followed the Great Cleft as far as the crater Hyginus : we now proceed to give the results of the observations of B. and M. upon its future course ; referring at the same time to the diagram in our last number. This crater, 3 miles in diam., and tolerably deep, with 6° or 70 of brightness, has its ring split by the cleft, which passes across the interior, with elevated edges, in such a manner that the continuity of its banks is nowhere interrupted. Of this they had an interesting proof upon one occasion in the waning moon, when the steady air admitted of a power of 300 : the interior of the crater was wholly in shade, with the exception of two minute but very brilliant lines of light in the position of the cleft, while the wall on the N.E. and W., where the cleft encountered it, was interrupted by a very narrow but perfectly black shadow. From the E. side of Hyginus issues an extremely small cleft, 4 or 5 miles in length, which was detected by Lohrmann, and seen, once only, by B. and M. After leaving this spot, the cleft, in its westward course, touches on five extremely small craters, or possibly only “longish circular widenings,” and is bordered on the S. by two broad flat hills; all these being objects of an exceedingly difficult character. Beyond the tenth crater the cleft becomes wider, flatter, and less regular, and ends as it began, at a long bill, at whose S.W. extremity a little crater (Agrippa b) is faintly perceptible. Its whole length is about 106 miles, its average breadth nearly 1 mile: the steeper are the more reflective parts; the light of the flatter ends losing itself in that of the surrounding surface. With the great achromatic at Dorpat, M. subsequently found that a great part of this cleft consisted of a chain of confluent roundish cavities. The plain S. of the cleft contains a few small craters of various sizes, two small dark spots and one larger, and one of a green hue, about 30 in brightness, and extending over about 3,600 square miles. On the N. the cleft is attended by a number of very low parallel chains of hills; one mass immediately N. of Hyginus shows a curious spiral arrangement; but generally they point S.W. or S.S.W., and this bearing is visible over a considerable area in this direction, overspread with minute banks and ridges, invisible excepting near the terminator, and usually only from 40 to 60 yards in height. Our authorities especially direct attention to the fact that in this region, where no deception can be

occasioned by foreshortening, the general parallelism of all chains of hills and lines of valleys is peculiarly evident: this bearing—"geognostically” towards 10h. (of a dial divided into 24h.) is visible throughout the Apennines, the Hæmus, the M. Vaporum and its neighbourhood, Ukert, Pallas, Bode (28), Julius Cæsar, Agrippa, Godin, Dionysius, and in part the M. Tranquillitatis itself: in many parts it exceeds any other direction as 30: 1, and between Mt. Hæmus and the cleft of Ariadæus, it is almost the exclusive one. They point out also another peculiarity, the great variety of local shading, or “colour," in this region under varied illumination. In Full Moon the higher of the ridges N. of Ilyginus come out with a reflective power of 4° or 5°, the interjacent valleys, with 3° or 31°, brighter than the levels of the M. Vaporum, and the darkest part of the neighbourhood does not lie here, but at the foot of some higher mountains E. of the cleft ; and even these are less dark than the spot Boscovich. On the other hand, about the time of the quadratures, a large blackish somewhat undefined spot comes out just between the two higher chains of mountains near Hyginus y (the two N. of that crater in our diagram) covering these ridges, whose summits are with difficulty visible in it, and contrasting singularly with the surrounding landscape. It is evident, on inspection, as B. and M. remark, that it cannot be shadow; nor can it be merely a feebler illumination, which could not in this way reduce to blackness the yellow, yellowish grey, and pale greenish hues of the lunar surface; so that we have here a colour variable with the phases, which appears to require some further explanation than merely varied reflection. The day and night are also the summer and winter of the moon; and consequently a change of colour whose period is that of a lunation may as well be the result of temperature as of light; and a careful examination of such regions seems especially suited to lead to some discoveries as to the physical economy of our neighbourworld. Had this been Schr's. conclusion, it would have been entirely in character with his general ideas, but proceeding from observers so little disposed to receive any evidence of change, it is worthy of pointed attention. Fortunately the district is one very well marked, easily found, and unaffected in appearance by libration.

The second great cleft, that of Ariadæus, lies W. of the preceding, and is described by B. and M. the reverse way, from W. to E. It was discovered by Schr., like the other, which it exceeds in length, breadth, and probably depth, though less easy to find on account of its more mountainous surroundings. It begins at a mountain Ariadæus y (see the diagram), and after a course of about 18 miles, receives another cleft coming from the S., 16 miles long, very narrow, and of inferior depth-à difficult object detected by B. and M. 23m. further, it strikes on the mountain Ariadeus B, without, however, perceptibly dividing it, as it had done a small ridge a little previously. On the other side of Bit recommences in the same direction, and passes through two minute craters, appearing here to be very deep. 14m. further on, it is interrupted by the mountain Ariadous a, till its traces are next recovered in a narrow ravine among the hills, in a somewhat altered direction. Henceforward it splits every elevation, great and small, in its way, although a high ridge, Silberschlag a, so compresses it that the separation can only be perceived with difficulty. Further on, the heights on either side are flatter, and it terminates in a small crater S. of Boscovich, after a course, windings included, of 113 miles. Gruithuisen observed a very minute prolongation of it, between Arago A and Ritter, for a considerable distance towards the equator. This, though confirmed by Kunowsky, was not made out by B. and M., but has since been seen by Kinau and Schmidt. If it is really a continuation of the great cleft, it may possess considerable selenological interest, as showing how much more effect the same cause has produced on a comparatively mountainous surface than on a depressed plain. Two other very minute clefts (if not three) between Sosigenes and Arago, and two more S. of Sabine (which had been seen by Lohrmann) belong to the M. Tranquillitatis. Schmidt has detected several others along this shore.

S.E, of Hyginus, and on the edge of the M. Vaporum, lies the crater Triesnecker, encompassed by a narrow equable wall, 14 iniles in diameter, and 5400 feet high on the E. On every side but the E. it is encompassed by long clefts, forming the most numerous group known to B. and M., some of which had been seen by G. B and y, the most distinct, form an angular junction near the wall: the whole could very seldom be seen at the same time. S is interrupted by a low ridge. Between B and y is a very difficult little crater. Though the connection and branching out of these clefts appeared to B. and M. unique on the moon, yet the similarity to a terrestrial river-system is very slight : there is no winding, or widening in either direction, and the interruption by a hill must negative any such idea.

Having thus given an abstract of B. and M.'s description of this curious region, we may find it worth while to compare it with the results obtained by other observers. First of all, the original discoverer, Schr., has given a long description, and a figure of the two principal clefts, which alone he saw, and two additional diagrams of the W. one. The name Hyginus

VOL. XII.—NO, II.

to bylongon the equablo inics

« AnteriorContinuar »