with tar; that tar water and pomades of tar are frequently employed in medicine, has extended its applications to therapeutics."

Many other efforts are still necessary. In point of fact the results thus far obtained are merely rough outlines, only first trials. So long as the world at large is not in possession of a simple, easy, and economical method, accessible to every one, which shall be capable of disinfecting immediately, and without inconvenience on the large or small scale, dejections and filth of all kinds, in dwellings as well as in privies or slaughter-houses; in dissecting-rooms and the like, as well as in the sick room, upon wounds, improvements will still be wanted; there will yet be room for new attempts. While recording those of to-day and those of yesterday upon the road already traversed, let us be careful not to diminish the ardor of the laborers in the future, who will finally endow civilization with a complete and general disinfection."

Finally, certain indispensable precautions must be followed, in order to obtain from the process of Corne and Demeaux its proper effect. It is evident, from having neglected some of these precautions, that different experimenters have been led to believe that the method is useless. Fine moulding plaster, and not the common article, should be employed. The coal-tar, which is mixed with it in the proportion of 2 to 4 parts to a hundred, by triturating or grinding, ought to impart to it a gray tint, without destroying its dry, pulverulent condition. Objects to be disinfected should be rolled in this powder until each point upon their surfaces has been brought in contact with it. Gangrenous or putrid sores should be covered with thick layers of it; by handfuls, several times per day. If one is treating pus, blood, dejections, or the like, enough of the powder should be added to form a paste of the mass, taking care to replace the first layer of powder by another as soon as it no longer absorbs any more. Mixed with oil to the consistence of a thick pap, it forms poultices of convenient application, if they are made thick and broad. Within the limits which have been indicated the mixture of coal-tar and plaster is a good disinfectant, and may be recommended for use in domestic economy as well as in hospitals. "What we have ourselves seen leaves no uncertainty of the reality of this property, nor of the possibility of its application." It remains only to draw from it reasonable, practical consequences, either taking the fact as it is, or by modifying and perfecting it.--Comptes Rendus, 1, 279.

* * * * *

[For corroborating testimony, received by the committee from various sources, the reader is referred to their report in question. Numerous other articles upon the subject, by different authors, may also be found in vol. xlix of the Comptes Rendus.-F. H. S.]

7. Decoloration of Indigo by Sesquioxyd of Iron.-[In the May number of this Journal we took occasion to maintain that the very interesting fact of the power of ferric salts to bleach solutions of indigo was first observed by Prof. H. Wurtz. Since then we have accidentally learned that this claim was erroneous, as will appear from the following statement made by Wohler some twenty years since. "When a solution of

indigo in sulphuric acid is mixed with salts of the sesquioxyd of iron and heated, it will be decolorized precisely as it would be by nitric acid.". (Annalen der Chemie und Pharmacie, 1840, xxxiv, 235; see also Gmelin's Handbook (Cavendish Soc. Edit.), xiii, 59.-F. H. S.]

II. GEOLOGY.

1. On Some Points in Chemical Geology; by T. STERRY HUNT, F.R.S. (Read before the Geol. Society of London, January 5th, 1859--published in the Quarterly Journal of the Society for November, 1859-and reprinted, with additional notes by the author, in the Canadian Naturalist for January, 1860.). In this paper the author discusses a number of questions which lie at the foundation of a true history of the chemistry of the earth's crust, and gives farther developments to some of his peculiar views, which were for the most part, first enunciated in this Journal. In regard to the metamorphism of sedimentary deposits, i. e., the conversion of sands, clays and marls into crystalline stratified rocks, the author, after distinguishing between local and normal metamorphism, insists upon the frequent interstratification of unchanged fossiliferous limestones among crystalline schists as evidence that heat has not been the only agent in the metamorphism, which has moreover been effected at temperatures not very elevated, and by the intervention of alkaline solutions, in the absence of which, sediments may be heated to the same degree without change.

The first announcement of this view will be found in this Journal for May, 1857 (vol. xxiii, p. 407), where the author, after describing some experiments with the alkaline silicates, expresses the opinion that "we have here the explanation of rock metamorphism in general." Farther inquiries into the action of the soluble alkaline silicates will be found in this Journal for March and May, 1858 (vol. xxv, pp. 287-437), where the subsequent experiments of Daubrée are cited in confirmation and extension of Mr. Hunt's theory of the normal metamorphism of sediments at comparatively low temperatures by the intervention of alkaline carbonates and silicates, which may be either liberated by the decomposition of the sediments themselves or derived from adjacent strata. These salts in solution permit the crystallization of feldspars and micas, or when alkaline bases are present only in smaller quantity, of kyanite, andalusite and staurotide, while by the intervention of protoxyd bases, garnet, epidote, chloritoid and chlorite are formed, and in the absence of the argillaceous element, pyroxene, olivine, serpentine and talc. In a subsequent note the author has however alluded to the probable direct formation of certain silicates of magnesia and lime, in open basins at the earth's surface and by reactions at the ordinary temperature. This Journal, March, 1860 (xxix, 284).

In the second place the author discusses the relations of plutonic to metamorphic sedimentary rocks, and concludes that the latter, becoming plastic under the influence of water and heat, may be displaced by disturbance and pressure, thus taking the form of intrusive rocks. Sediments altered in situ he distinguishes as indigenous, and those displaced as exotic plutonic rocks. The conclusions of Scrope, Scheerer and Elie de Beaumont, supported by the late observations of Daubrée and Sorby, as to the aqueo-igneous fusion of these rocks, are fully admitted.

In the third place the author discusses the theories of Phillips, Bunsen and Durocher, as to the origin of intrusive rocks, and rejecting the notion that these are derived from the supposed fluid interior of the earth, re

gards them as in all cases, fused and displaced sediments. He proceeds to show that the action of waters removing from permeable strata their soda, lime and magnesia, brings these to the composition of granitic rocks, while the finer and less permeable sediments, retaining their protoxyd bases, give rise by subsequent alterations to basic rocks with triclinic feldspars and pyroxene. Soda being preeminently the soluble alkali, has been gradually removed from disintegrated feldspathic rocks under the influence of water and carbonic acid, and the carbonate of soda thus formed has by its reaction with the lime salts of the ancient ocean, given rise to sea-salt and to the carbonate of lime with which the limestones have been built up. The aluminous silicate set free in the decomposition of the feldspars is thus the equivalent of the earthy carbonates and sea-salt which are formed. Hence we find that in the oldest known crystalline rocks, those of the Laurentian series, soda feldspars are abundant, micaceous schists rare, and argillites or silicates of alumina deficient in alkali are unknown, while in higher formations, argillites and schists with kyanite, chiastolite and staurotide abound, as well as chlorite, chloritoid, muscovite, garnet, epidote, etc., showing a great excess of aluminous silicate over the alkali required to form feldspars.

These views have already appeared in a communication from the author in this Journal (vol. xxv, p. 436) where also the action of organic matters in deoxydizing, dissolving and removing oxyd of iron from certain strata to be accumulated in others, is discussed and illustrated by a consideration of the iron deposits of various ages. The existence of beds of iron ore in the Laurentian rocks, not less than the graphite and metallic sulphurets which these contain, is by the author regarded as evidence that organic life existed at the period when these rocks were deposited. As Mr. Hunt has elsewhere explained, he supposes the condition of the cooling globe to have been one of thorough oxydation, and regards all processes of reduction or deoxydation as dependent either directly or indirectly upon organic life. In regard to iron oxyd however he remarks that its solution may sometimes be due to mineral acids, from volcanic or other sources; such solutions, and others from the oxydation of pyrites, may be decomposed by alkaline or earthy carbonates and give rise to iron deposits. A similar process with aluminous solutions will serve to explain the origin of corundum, beds of emery, and aluminous iron ores. In regard to the agency of organic matters in the formation of iron deposits we may here remark that a reviewer in this Journal (xxv, 245) in noticing Mr. Hunt's observations on this subject contained in his Geological Report for 1856, writes as if Mr. H. had appropriated the views of Bischof. In truth neither Bischof nor Hunt ever claimed any originality in bringing forward a principle which has long been understood, and which they have only attempted to extend and develope. We may here observe that the same reviewer fails to apprehend Mr. Hunt's views on the formation of crystalline rocks, when he says that Bischof and Hunt agree in supposing all rocks to be formed by chemical agencies in the presence of water, and that therefore the latter cannot claim originality. Now upon the point in question there is little or no affinity between the views of the two writers, for the simple reason that Bischof seems never for a moment to apprehend the nature of the great problem which Mr. Hunt has under

taken to solve, but with Dana regards normal metamorphism as pseudomorphism on a grand scale. The ingenious speculations of Bischof and others on the possible alteration of mineral species by the action of various saline and alkaline solutions may pass for what they are worth, although we are satisfied that by far the greater part of the so-called cases of pseudomorphism in silicates are purely imaginary, and when real are but local and accidental phenomena. Bischof's notion of the pseudomorphism of silicates like feldspars and pyroxene presupposes the existence of crystalline rocks, whose generation this neptunist never attempts to explain, but takes his starting point from a plutonic basis.

The problem to be solved, as we have elsewhere insisted, is the conversion of sands, clays and marls, (consisting of silica, silicates of alumina, carbonates of lime, magnesia and oxyd of iron, derived by chemical and mechanical agencies from the ocean waters and pre-existing crystalline rocks,) into aggregations of crystalline silicates. These metamorphic rocks, once formed, are liable to alteration only by local and superficial agencies, and are not, like the tissues of a living organism, subject to incessant transformations, the pseudomorphism of Bischof and Dana. As yet, Mr. Hunt is the only one who has attempted a rational explanation, based on experiments, of the problem of the conversion of sedimentary strata into crystalline rocks, and his views, whether true or false, are to be judged by themselves, and not by comparison with those of Bischof or any other writer. Among the geologists who since the time of Hutton, have best comprehended the nature of the problem of rock metamorphism, are Boué, Virlet and Delanouë. We hope at an early day to discuss in the pages of this Journal, the question of mineral pseudomorphism, as well as the history and theory of metamorphism.

Passing from plutonic to volcanic phenomena, Mr. Hunt proceeds to develope the views of Babbage and Herschel as to the effects of the internal heat upon deeply buried sediments. Babbage has shown that the expansion of the sedimentary rocks by heat may cause great vertical movements, while in the subsequent fusion of the heated sediments Herschel finds an explanation of volcanic phenomena. These views the author adopts, and enters into a consideration of the relations which must take place between silica and silicates, carbonates, sulphates, chlorids and organic matters in the presence of water at an elevated temperature. To azotized organic substances and to the ammonia condensed in argillaceous strata, he ascribes, with Bischof, the ammoniacal salts of volcanoes.

In considering the metamorphism of the strata, which must always precede volcanic action, we are not to lose sight of a process which will, in its results, be the reverse of that insisted upon by Babbage. It is the great contraction which must result, not only from the solidification of the porous sediments, but from the condensation attendant upon chemical combination, by which they are converted into silicates of high specific gravity, such as pyroxene, garnet, epidote, chloritoid and chiastolite. In this way, as remarked by Mr. Hunt in his lectures before the Smithsonian Institution at Washington last winter, we may realize, to a certain extent, Elie de Beaumont's notion of a shrinking of the earth's nucleus, and find an explanation of many phenomena of subsidence and corrugation, although with Herschel we are to attribute these for the most part to "the disturb

ance of the equilibrium of pressure consequent upon the transfer of sediments while the yielding surface reposes upon a mass of matter partly liquid and partly solid.'

We conclude with the following extracts, and with two notes appended to the Canadian reprint of Mr. Hunt's papers, in one of which he calls attention to the remarkable work of Keferstein, whose ingenious views, too much in advance of his time, have hitherto been overlooked.

"The metamorphism of sediments in situ, their displacement in a pasty condition from igneo-aqueous fusion as plutonic rocks, and their ejection as lavas with attendant gases and vapors are then all results of the same cause, and depend upon the differences in the chemical composition of the sediments, the temperature, and the depth to which they are buried: while the unstratified nucleus of the earth, which is doubtless anhydrous, and according to the calculations of Messrs. Hopkins and Hennessey, probably solid to a great depth, intervenes in the phenomena under consideration only as a source of heat."*

"The volcanic phenomena of the present day appear, so far as I am aware, to be confined to regions covered by the more recent secondary and tertiary deposits, which we may suppose the central heat to be still penetrating (as shown by Mr. Babbage), a process which has long since ceased in the paleozoic regions. Both normal metamorphism and volcanic action are generally connected with elevations and foldings of the earth's crust, all of which phenomena we conceive to have a common cause, and to depend upon the accumulation of sediments and the subsidence consequent thereon, as maintained by Mr. James Hall in his theory of mountains. The mechanical deposits of great thickness are made up of coarse and heavy sediments, and by their alteration yield hard aud resisting rocks; so that subsequent elevation and denudation will expose these contorted and altered strata in the form of mountain chains. Thus the Appalachians of North America mark the direction and extent of the great accumulation of sediments by the oceanic currents during the whole

* "The notion that volcanic phenomena have their seat in the sedimentary formations of the earth's crust, and are dependent upon the combustion of organic matters, is, as Humboldt remarks, one which belongs to the infancy of geognosy. In 1834 Christian Keferstein published his Naturgeschichte des Erdkörpers, in which he maintains that all crystalline non-stratified rocks, from granite to lava, are products of the transformation of sedimentary strata, in part very recent, and that there is no well-defined line to be drawn between neptunian and volcanic rocks, since they pass into each other. Volcanic phenomena according to him have their origin, not in an igneous fluid centre, nor an oxydizing metallic nucleus, but in known sedimentary formations, where they are the result of a peculiar process of fermentation, which crystallizes and arranges in new forms the elements of the sedimentary strata, with evolution of heat as an accompaniment of the chemical process. (Naturgeschichte, vol. i, p. 109, also Bull. Soc. Geol. de France (1) vol. vii, p. 197).

These remarkable conclusions were unknown to me at the time of writing this paper, and seem indeed to have been entirely overlooked by geological writers; they are, as will be seen, in many respects an anticipation of the views of Herschel and my own; although in rejecting the influence of an incandescent nucleus as a source of heat, he has, as I conceive, excluded the exciting cause of that chemical change, which he has not inaptly described as a process of fermentation, and which is the source of all volcanic and plutonic phenomena. See in this connection my paper On the Theory of Igneous Rocks and Volcanoes, in the Canadian Journal for May,

1858."