range at high angle. There can be no doubt, therefore, that all the strata of this foot-hill region, including the slates, underdip the range at high angle. Evidently, therefore, the cleavage planes of these slates are parallel to the stratification planes instead of cutting through them at high angle as is most common.

The diverse relation of the cleavage to the stratification planes I explain as follows: In a thick mass of very fine sediments mashed together horizontally it is evident that the surface and upper portions would first be thrown into one or more close folds by which the strata are brought into a nearly perpendicular position, and then these would be thinned and extended vertically by the pressure as already shown in the previous portion of this paper: but the deeper portions would be less and less folded, until, very deep, the folding would cease altogether and the mashing would be by thickening only and not by folding. I have rudely represented these facts in the diagram, fig. 2, in which the parallel, nearly vertical lines, represent the cleavage. In such a mass of horizontally squeezed fine sediments, therefore, the cleav

age of the upper parts would be parallel with the strata while that of the lower parts would be perpendicular or nearly so to the strata. If, therefore, the upper parts only should be exposed by denudation we would have an example of cleavage parallel to the strata, and we might be in

2.

doubt whether to call the planes cleavage-planes or fine lamination-planes; but if greater denudation should expose the deeper portions we would have an example of cleavage-planes cutting through the lamination-planes at a high angle and therefore very distinct from them."

3. It is evident from the above that in many cases the thickness of the strata as we now find them may be very different from that of the original sediments. In estimating the latter, therefore, we must make due allowance for the great thinning in some cases and thickening in others produced by pressure.

4. In my paper on the formation of the great features of the earth surface, already referred to, I have attributed mountain elevation to horizontal crushing. Prof. Dana, however, thinks that, although the idea of plication is evidently included in my view, yet it ought to have a larger place than my words seem to give it for the amount of elevation by plication is many times ("ten-fold") greater than by simple crushing.

*Am. Journ., III, v, 428.

Perhaps I ought to have been more explicit in my statement, but it seemed to me unnecessary, because on the assumption of a solid earth the amount of elevation would be the same, or nearly the same, whether, by the horizontal pressure, the strata be thrown into closed folds (as is most common in mountain chains) or only thickened without folding. If every two or three parts in horizontal extent of sediments be crushed into one part, there must be a corresponding thickening of the whole squeezed mass, and, therefore, a corresponding elevation of the surface, whether the strata be closely folded or only thickened without folding. In reality, doubtless, both occur in every case; close folding in the upper parts and thickening without folding in the deeper parts of the same squeezed mass. In fact it is impossible that the folding should occur above without a corresponding crushing and thickening below.

Again, I am satisfied that Prof. Dana greatly under-estimates the amount of elevation by simple mashing as compared with folding: 1st, because folding is a superficial phenomenon and therefore always exposed to view, while crushing without folding is deep seated and only rarely exposed; 2d, because folding is always revealed by stratification, while crushing is only sometimes revealed by cleavage, for this structure is only developed in suitable materials; and 3d, because even after folding, extension upward may take place by mashing together of the folds, as I have shown in the early part of this paper.

have spoken thus far of closed folds. In open folds such as occur on the skirts of mountain chains where the horizontal crushing has not been sufficient to bring the folds together, the case might seem to be different; but even in these there must be a mashing of the strata below each anticlinal and proportioned to its height, unless we assume a hollow arch beneath, or else such an arch supported by a liquid, an assumption which is expressly set aside in my paper.

Berkeley, Oct. 11, 1875.

ART. XXXVIII.-Brief Contributions to Zoology from the Museum of Yale College. No. XXXVII-Description of Mancasellus brachyurus, a new fresh water Isopod; by O. HARGER.

*

THE genus Asellopsis was proposed by the writer for the reception of Asellus tenax Smith, on account of the absence of mandibular palpi. A second species of this interesting genus has lately been collected by Mr. Fred. Mather, in Rockbridge

*This Journal, III, vol. vii, p. 601, 1874.

Co., Virginia. Since the name Asellopsis proves to have been preoccupied I propose in its place Mancasellus,* retaining M. tenar as the typical species, while the new species may be called M. brachyurus, from the short caudal stylets. This species resembles M. tenax, described and figured in the Report of the United States Commissioner of Fish and Fisheries, Part II, Report for 1872-3, p. 659, plate I, fig. 3, differing principally from it in the following points: The lateral margins of the head are entire; the proximal segment of the caudal stylets is short, being but little longer than the third segment of the antennæ; the rami are also short, the inner being much stronger and somewhat longer than the outer; in the males the propodus of the first pair of legs is armed with a prominent acute tooth on the palmar margin near the base, and, in the appendages of the seventh segment, the terminal portion of the outer pair is smaller and less expanded externally than in M. tenax, and the distal segment of the internal ramus of the inner pair is but little swollen at the base, and approaches the form seen in Asellus communis Say. The largest specimen measures 16mm, in length exclusive of the antennæ and caudal stylets. The locality is worthy of mention as being on the Atlantic side of the Appalachian water-shed while M. tenax is yet known only from the Lakes.

ART. XXXIX.-Professor Tyndall on Germs.t

THE author refers, in an introduction, to an inqury on the decomposition of vapors and the formation of actinic clouds by light, whereby he was led to experiment on the floating matter of the air. He refers to the experiments of Schwan, Schröder and Dusch, Schröder himself, to those of the illustrious French chemist Pasteur, to the reasoning of Lister and its experimental verification, regarding the filtering power of the lungs; from all of which he concluded, six years ago, that the power of developing life by the air, and its power of scattering light, would be found to go hand in hand. He thought the simple expedient of examining by means of a beam of light, while the eye was kept sensitive by darkness, the character of the medium in which their experiments were conducted, could not fail to be useful to workers in this field. But the method has not been much turned to account, and this year he thought it worth while to devote some time to the more complete demonstration of its utility.

* From mancus, maimed, and Asellus.

On the Optical Deportment of the Atmosphere in reference to the Phenomena of Putrefaction and Infection. Abstract of a paper read before the Royal Society, January 13th, by Professor Tyndall, F.R.S. From Nature of Jan. 27 and Feb. 3.

He also wished to free his mind, and if possible the minds of others, from the uncertainty and confusion which now beset the doctrine of "spontaneous generation." Pasteur has pronounced it "a chimera," and expressed the undoubting conviction that, this being so, it is possible to remove parasitic diseases from the earth. To the medical profession, therefore, and through them to humanity at large, this question is one of the last importance. But the state of medical opinion regarding it is not satisfactory. In a recent number of the British Medical Journal, and in answer to the question, "in what way is contagium generated and communicated?" Messrs. Braidwood and Vacher reply that, notwithstanding "an almost incalculable amount of patient labor, the actual results obtained, especially as regards the manner of generation of contagium, have been most disappointing. Observers are even yet at variance whether these minute particles, whose discovery we have just noticed, and other disease germs, are always produced from like bodies previously existing, or whether they do not, under certain favorable conditions, spring into existence de

novo."

With a view to the possible diminution of the uncertainty thus described, the author submits, without further preface to the Royal Society, and especially to those who study the etiology of disease, a description of the mode of procedure followed in this inquiry, and the results to which it has led.

A number of chambers, or cases, were constructed, each with a glass front, its top, bottom, back and sides being of wood. At the back is a little door which opens and closes on hinges, while into the sides are inserted two panes of glass, facing each other. The top is perforated in the middle by a hole two inches in diameter, closed air-tight by a sheet of india-rubber. This sheet is pierced in the middle by a pin, and through the pin-hole is passed the shank of a long pipette ending above in a small funnel. A circular tin collar two inches in diameter and one inch and a half high, surrounds the pipette, the space between both being packed with cotton-wool moistened by glycerine. Thus the pipette, in moving up and down, is not only firmly clasped by the indiarubber, but it also passes through a stuffing box of sticky cottonwool. The width of the aperture closed by the india-rubber secures the free lateral play of the lower end of the pipette. Into two other smaller apertures in the top of the case are inserted, air-tight, the open ends of two narrow tubes, intended to connect the interior space with the atmosphere. The tubes are bent several times up and down, so as to intercept and retain the particles carried by such feeble currents as changes of temperature might cause to set in between the outer and the inner air.

The bottom of the box is pierced with two rows, sometimes with a single row of apertures, in which are fixed, air-tight, large test-tubes, intended to contain the liquid to be exposed to the action of the moteless air.

On Sept. 10 the first case of this kind was closed. The passage of a concentrated beam across it through its two side windows

then showed the air within it to be laden with floating matter. On the 13th it was again examined. Before the beam entered, and after it quitted the case, its track was vivid in the air, but within the case it vanished. Three days of quiet sufficed to cause all the floating matter to be deposited on the sides and bottom, where it was retained by a coating of glycerine, with which the interior surface of the case had been purposely varnished. The test-tubes were then filled through the pipette, boiled for five minutes in a bath of brine or oil, and abandoned to the action of the moteless air. During ebullition aqueous vapor rose from the liquid into the chamber, where it was for the most part condensed, the uncondensed portion escaping, at a low temperature through the bent tubes at the top. Before the brine was removed little stoppers of cotton-wool were inserted in the bent tubes, lest the entrance of the air into the cooling chamber should at first be forcible enough to carry motes along with it. As soon, however, as the ambient temperature was assumed by the air within the case, the cotton-wool stoppers were removed.

We have here the oxygen, nitrogen, carbonic acid, ammonia, aqueous vapor, and all the other gaseous matters which mingle more or less with the air of a great city. We have them, moreover, "untortured" by calcination and unchanged even by filtration or manipulation of any kind. The question now before us is, can air thus retaining all its gaseous mixtures, but self-cleansed from mechanically suspended matter, produce putrefaction? To this question both the animal and vegetable worlds return a decided negative.

Among vegetables, experiments have been made with hay, turnips, tea, coffee, hops, repeated in various ways with both acid and alkaline infusions. Among animal substances are to be mentioned many experiments with urine; while beef, mutton, hare, rabbit, kidney, liver, fowl, pheasant, grouse, haddock, sole, salmon, cod, turbot, mullet, herring, whiting, eel, oyster have been all subjected to experiment.

The result is that infusions of these substances exposed to the common air of the Royal Institution laboratory, maintained at a temperature of from 60° to 70° Fahr., all fell into putrefaction in the course of from two to four days. No matter where the infusions were placed, they were infallibly smitten. The number of the tubes containing the infusions was multiplied till it reached six hundred, but not one of them escaped infection.

On the other hand, in no single instance did the air, which had been proved moteless by the searching beam, show itself to possess the least power of producing Bacterial life or the associated phenomena of putrefaction. The power of developing such life in atmospheric air, and the power of scattering light, are thus proved to be indissolubly united.

The sole condition necessary to cause these long-dormant infusions to swarm with active life is the access of the floating matter of the air. After having remained for four months as pellucid as