tains, by of the of mountains or plateaus on their edges. If any portion the proof the crust were unsupported by the nucleus, its ten- duction dency would be to support itself on the principle of the of mounarch. We cannot compare its condition to that of a thin, subsiunsupported, and brittle egg-shell, as has been done by dence of M. Elie de Beaumont, for the attractions to which the solid portions shell of the Earth is subjected, acting very nearly perpendi- Earth's cularly to the tangent plane at any point of its inner sur- crust. face, acts precisely in the direction best adapted for securing its stability. On the contrary, a small, round object like an egg-shell, at the Earth's surface, is subjected to parallel pressures, and is thus placed under more unfavourable conditions for stability. If we consider two arches of equal dimensions and Illustrastrength, one with a mass of fluid pressing down on its tion extrados, the other with a mass of fluid pressing upwards from the on its intrados, the head of fluid producing pressure equiliin brium of both cases being equal to the depth of the fluid over the arches. first arch, it is manifest that the second arch would be far more readily burst upwards than the other would be erushed downwards. It is well known to engineers that arches made to sustain incredible pressures from above, may be easily "blown up" by a comparatively moderate pressure from below. against adequate The forces resulting from the expansion of the nu- The cleus, and its pressure against the shell, are, as well pressures as the action of gravitation, perpendicular to the tan- exerted by the gent planes of the shell, but while the latter acts in fluid nuthe direction most favourable to stability, the former act cleus of in the direction most favourable to rupture, and would, the Earth therefore, be far more likely to be effective in producing the solid disturbances of the Earth's crust, and above all the ele- crust, vation of the lines of mountains, which impart such a present peculiar character to its general configuration. In my Re- causes searches on Terrestrial Physics, I have in some measure for pheconsidered the action of such a pressure, combined with noniena another that would result from a tendency in the nucleus tion. to change its figure, and I have shown that if the former happened to be small compared to the latter, a zone of least disturbance might exist on the Earth's surface, for the position of the boundaries of which formulæ are assigned. As no trace seems to exist of such a zone from geodesical measurements, I was led to infer that the general pressure predominated over the variable pressure, and, therefore, that lines of elevation on the Earth's surface. of eleva should not present any marked relation of parallellism, either to the equator or to the meridians. It is satisfactory to find that this theoretical inference is confirmed by a conclusion of M. Elie de Beaumont, in the work already quoted. If the lines of elevation of the Earth's surface are grouped, so as to form, for the most part, a series of diametral lines to each figure of a network of regular pentagons, I cannot see any reason why such a symmetrical network might not be formed far more readily by the pressure of the nucleus acting outwardly against the shell, than by the subsidence of the latter inwards. The more regular and symmetrical the arrangements of the mountain systems, the more difficult it appears to reconcile them with mere subsidence, and the more easily do these arrangements seem to admit of explanation by the action of purely elevatory forces. The analogy between an interior, expanding, elevatory force, which separates the parts of a mass, and the molecular forces, which cause portions of certain rocks—for instance, basalt-to split into polygonal prisms, is far more clearly manifest, than between these phenomena and the crushing force which would accompany an action of subsidence. Lines of least resistance to separation or simple fracture, are more easily determined by the action of these forces, than lines of easiest crushing or squeezing, and greater symmetry might be fairly expected in the distribution of the former than in that of the latter. ART. III.-Note on the differences of level (seiches) observed by M. Stabrowski on Lake Onéga in Russia. By HENRY HENNESSY. THE HE phenomena briefly described by M. Stabrowski in the Comptes rendus of the French Academy for last July, present some relations of resemblance to those occurring on the surface of Lough Erne, the physical explanation of which is contained in a letter addressed by me to the President of the Royal Irish Academy, which appears in the Proceedings of that body.' Both at Lough Erne and Lake Onéga, the abnormal 1 Vol. vi., p. 279. condition of the surface of the water is due to atmospheric disturbance; but while in the former the action of the air seems to be entirely dynamical, in the latter its mode of action, and the resulting effects, present a statical character. The transitory wave of translation, which sometimes unexpectedly beats against one of the shores of our Irish lake, is due, as I have shown, to the action of descending currents of air from the hills at the opposite side; but Lake Onéga appears to act under changes of atmospheric pressure, like a differential barometer. It possesses all the conditions essential for this purpose, being long and narrow. The result is, that accidental differences of atmospheric pressure at its extremities would produce very observable changes in the water level. The rising of the water at one side of the lake is usually accompanied by a fall in the barometer, and vice versa. The seiche is always the precursor of wind [horizontal currents], and the oscillations of the surface of the lake enable the natives to foretell the direction and force of the winds. ART. IV. On the formation of several Acids of the WH animal HENEVER we submit animal or vegetable sub- Action of stances to the action of heat in close vessels, we heat obtain three classes of products-gaseous, liquid, and upon solid. The gaseous products consist chiefly of carbonic and veacid, carbonic oxide, olefiant gas, and marsh gas. The getable liquid products consist of water holding certain liquid and some few solid bodies in solution. Another portion in close of the liquid products insoluble in water, and holding vessels. the chief part of the solid bodies in solution, forms a mass An abstract of the chief results contained in this paper was read at the Dublin meeting of the British Association, August 27, 1857. sub stances Classes produced. as tar. of a more or less oily or butyraceous consistence, known The bodies held in solution by the water and the constituents of the tar are very numerous and various. But their relative proportions, and in some respects their nature also, depend upon the kind of body submitted to distillation, and upon the temperature at which the distillation takes place. The latter circumstance, indeed, not only affects the constituents of the tar and the bodies held in solution in the water, but also the gaseous products. If the distillation be effected at a very low temperature, scarcely any or no gas will be produced; if at a very high temperature, abundance of gas, and scarcely any liquid or solid products, will be formed. The liquid and solid products may be classified under of bodies four heads: 1. bases; 2. acids; 3. alcohols, ethers, and similar compounds; and 4. carbo-hydrogens. Bases are the result of the decomposition of azotic bodies, and their amount and number will therefore depend upon the quantity of nitrogen in the substances operated upon. Animal bodies, such as bones, blood, etc., will accordingly yield more than vegetable substances. The precise conditions upon which the formation of acids depends are not well understood; but it is evident that the substances which yield them must contain if oxygen, we except one, hydrocyanic acid, which contains nitrogen, and is accordingly formed most abundantly in the distillation of animal substances. The third class of bodies appear to be most readily formed from woody and amylaceous substances. The fourth are formed from all indifferently, though doubtless different kinds are produced from each substance distilled. Effects of tempera distillation. Generally speaking, it would appear that the effect the vari- of increasing the temperature of distillation is to lower ation of the atomic weight of the bodies produced. Thus, for ture of example, at comparatively very high temperatures the bases consist almost entirely of ammonia; at still higher temperatures, even this will be in part converted into cyanogen or totally decomposed. At comparatively low temperatures, several of the compound ammonias will also be produced, such as methylamine, ethylamine, aniline, etc. Similarly, among the hydrocarbons resulting from distillation at a low temperature, we have a large proportion of solid bodies, and a large proportion of the liquid ones have very high boiling points. The hydrocarbons produced at a high temperature, on the other hand, are chiefly liquid; and we may even carry the temperature high enough to get them in great part as gases or liquids with extremely low boiling points, or even to decompose them altogether, and get as our chief volatile product marsh gas. We know as yet too little about the circumstances affecting the production of the second and third classes of products, to speak positively upon the effect of temperature upon them; but there can be no doubt that it is similar to that exerted upon the bases and carbohydrogens. products been The substances whose products of distillation have Subbeen hitherto studied, are wood, coal, bituminous shale, stances and bones. The first yields the largest proportion of whose bodies belonging to class 3; the latter appears to give of distilthe largest proportion of bases. The products of another lation substance, peat, can now be added. This substance have stands intermediate between wood and coal, partaking studied. of the character of the one or of the other, according as we operate upon the light moor peat, in which the vegetable structure of the plants from which it was formed is still visible, or upon the compact earthy peats, in which all trace of organized structure has disappeared. The products are probably more numerous and various than even those of wood, the more so because the temperature of distillation of peat is perhaps lower than that at which the distillation of any other bodies distilled on a manufacturing scale is effected. searches techno Mr. Rees Reece proposed, about seven or eight years Connecago, to effect the distillation of peat in a novel manner, tion of with the view of obtaining certain of the products for present commercial purposes. This process was made the sub- reject of an investigation, in which I was engaged, while with a chemist to the Museum of Irish Industry, in the former. year 1850, and although of an altogether technological cha- logical racter, it afforded me during its progress an opportunity investiof seeing that the complete investigation of the products gation. from a scientific point of view would be extremely interesting and important. Among the observations which I then made were, the detection of butyric acid, cyanide of ammonium, and cyanide of methyl, or acetonitrile CH,N, among the products of distillation, and the probability of the presence of other hydrocyanic ethers or nitriles. These observations were not mentioned in the report of the investigation published as a par |