dependent not on the actual quantity of colored material, but on the relative proportion of the solvent. Diagrams of the changing appearances of sulphocyanid of iron, of chlorid of copper, and of chlorid of cobalt were exhibited.

13. On several new Methods of detecting Strychnia and Brucia; Experiments on Animals with Strychnia, and probable reasons for non-detection of Strychnia in certain cases; and a new method of instituting postmortem researches in Strychnia; by Mr. T. HORSLEY, (Proc. Brit. Assoc., Aug. 1856; Ath. No. 1503.)—In the first lecture, Mr. Horsley observed that the circumstances attending Palmer's trial induced him to make a series of experiments on the subject, and he tried the effects of a precipitant formed of one part of bichromate of potash dissolved in fourteen parts of water to which was afterwards added two parts in bulk of strong sulphuric acid. This being tried upon a solution of strychnine, the bulk was entirely precipitated in the form of a beautiful golden-colored and insoluble chromate. The experiment, as performed by Mr. Horsley, was very interesting, and scarcely a trace of bitterness was left in the filtered liquor. He did not claim to have originated this discovery of the use of a chromic salt and an acid liquor; but the point to which he called attention was the essential difference in the mode of application, and he maintained that it was as much out of the power of any human being to define the limit of sensibility which he had attained, as it would be to count the sands or to measure the drops of the ocean. Taking thirty drops of a solution of strychnia containing half a grain, he diluted it with four drams of water. He then dropped in six drops of a solution of bichromate of potash, when crystals immediately formed, and decomposition was complete. Splitting up the half grain of strychnia into millions. of atoms of minute crystals, he said that each of these atoms, if they could be separated, would as effectually demonstrate the chemical characteristics of strychnia as though he had operated with a pound weight of the same. He then showed the chemical reaction with those crystals. Dropping a drop of liquor containing the chromate of strychnia into an evaporating dish and shaking it together, he added a drop or two of strong sulphuric acid, and showed the effect as previously noted. He next showed the discoloration produced in chromate of strychnia and chromate of brucia by sulphuric acid, the former being changed to a deep purple and then to a violet and red. It had been asserted since the trial of Palmer that the non-detection of strychnine in the body of John Parsons Cook was owing to the antimony taken by the deceased having somewhat interfered with the tests. Such a supposition was, in his (Mr. Horsley's) opinion, absurd. Nothing, he considered, could more incontestably disprove the fallacy than either of two new tests which he then performed. These he considered double tests, because they had first the obtainment of a peculiar crystalline compound of strychnine, which was afterwards made to develop the characteristic effects by which strychnine is recognized. Mr. Horsley next related a series of experiments which he had made on animals with strychnine, and entered into the probable reasons for its non-detection in certain cases, although (as he had just shown before) a method of detecting infinitesimal quantities of strychnia by tests. Having procured three rats at seven o'clock P. M., he (assisted by Dr,

Wright) gave each rat a quarter of a grain of powdered strychnia, and two hours afterwards a quarter and half a grain more to one of the three. Next morning at four o'clock they were all alive, and had eaten food (bread and milk) in the night, but at seven, or a few minutes after, they were all dead. The longest liver was one of the rats that had had only a quarter of a grain. In about three hours afterwards he applied the usual test, but could not detect the least indication of strychnine in the precipitate. There was, moreover, a total absence of bitterness in all the liquor. He tried every part of the bodies of the rats with the like results. What, then, became of the strychnine? Had it been decomposed in the organism, and its nature changed, as Baron Liebig intimated? As to the nondetection of strychnine, he thought it not improbable that the strychnine might have become imbibed into the albumen or other solid matter, and so abstracted from the fluid, forming by coagulation (say, for instance, in the blood) a more or less insoluble albuminate. This idea had occurred to him from noticing the coagulation of the glairy white of egg with strychnine, and the fact of his not recovering the full quantity of the alkaloid whenever he had introduced it. At any rate, it merited consideration. In his second experiment he administered three-quarters of a grain of strychnia to a wild rat, but the animal evinced little of the effects of *the poison, and it was purposely killed after five days. His third experiment was with two grains of strychnia, administered as a pill wrapped up in blotting-paper, to a dog-a full-sized terrier. It was apparently quite well for five hours, when the operator went to bed, but was found dead next morning, but lying apparently in the most natural position for a dog asleep. When taken up blood flowed freely from its mouth. On opening the animal (continued Mr. Horsley) I found the right ventricle of the heart empty of blood, whilst the left was full, some of the blood being liquid and some clotted. The stomach was carefully secured at both its orifices, and detached. On making an incision, I was surprised at not seeing the paper in which I had wrapped the pill, naturally expecting it would have been reduced to a pulp by the fluid of the stomach. I, therefore, sought for it, and lo! here it is, in precisely the same condition as when introduced into the gullet of the dog, and containing nearly all the strychnine. I have been afraid to disturb it until I had exhibited it to you, and now I will weigh the contents, and ascertain how much has been absorbed or dissolved. This experiment is important as showing the small quantity of strychnia necessary to destroy life; and, had I not been thus particular to search for the paper envelope, it might, possibly, have led to a fallacy, as I must have used an acid, and that would have dissolved out the strychnia, and the inference would have been that it was obtained from the contents of the stomach, whereas it had never been diffused. In this case, also, none of the absorbed strychnia was detectable in the blood or any part of the animal, although the greatest care was observed in making the experiments. The lecturer, who was listened to throughout with great attention, added that he had made further experiments, which he thought proved that it was highly probable a more or less insoluble compound of organic or animal matter with strychnia is found.

II. GEOLOGY.

1. On the Spongeous Origin of the Siliceous Bodies of the Chalk Formation; by J. S. BOWERBANK, (Proc. Brit. Assoc., August, 1856; Ath. No. 1505.)—The author attributes the whole of the numerous strata of nodular and tabular flints to vast quantities of spongeous bodies that existed in the seas of those remote periods. The elective attraction of the animal matter of the sponges inducing the deposit of the silex, which in the first instance is always in the form of a thin film surrounding the skeleton of the sponge, and from which successive crops of calcedonic crystals proceed, until the solidification of the whole is effected. The tabular form is accounted for on the presumption that the sponges originating the deposit grew on a more consolidated bottom than the tuberous ones, and that they therefore developed themselves in a lateral direction instead of in an erect position, and on approximating each other were cemented together, and thus formed continuous beds of considerable extent; and the author illustrated this portion of his subject by the production of four recent sponges of the same species, which, by being placed in contact while in the living state, became firmly united to each other within eighteen hours, ultimately forming one sponge. The occurrence of the shells of Echinoderms and of bivalve shells filled with flint was accounted for on the same principle; and the author produced recent bivalve shells, in a closed condition, completely filled with recent sponges of the same species as the sponges of commerce. The loose specimens of fossil sponges included in the Wiltshire flints were explained on the principle that, although sponges of the same species readily adhere to each other when placed in contact, those of different species never unite, however closely they may be pressed together. The author concluded his paper by applying the same principles to the siliceous deposits of the whole of the geological formations which were of aqueous origin.

2. On some Palaeozoic Starfishes, compared with Living Forms; by J. W. SALTER, (Proc. Brit. Assoc., August, 1856; Ath. No. 1505.)-The object of the communication was chiefly to exhibit some new forms of Asteriadæ, from the Upper Silurian rocks, which have all the aspect of Ophiuridæ, but are essentially distinguished by the number of ossicles which go to form a single segment of the arms,-the lower surface showing the characteristic double row of ambulacral bones (in this case flat plates,) and the upper being composed either of two or more rows of plates, while the Ophiuridae have a single plate above, and one below. There is, however, the closest similarity to the latter family in the length of the arms and the restriction of the disc (Protaster, Forbes), as well as in the great length of the spines on the margin (Palæocoma), while in the pentagonal form and simply plated integument of another genus (Palasterina), there is a much nearer approach made to the Asteriscus or Palmipes roseus than to any other type of living starfish. It is to this group that the fossils are supposed to belong; and to some of the species which have the disc little developed, or quite absent, there is a strong resemblance in a Lower Silurian form originally described by Forbes as Uraster, but which better specimens show to have had but two rows of suckers, and the avenues bordered by very large plates. The name Pa

læaster is proposed for this group, which is represented by four or five species. The genera are;-Palæaster (Salter), without disc, avenues deep, Upper and Lower Silurian, 4 species; Palasterina (ib.), pentagonal, disc moderate, Up. Sil., 1 species; Palæocoma (ib.), no disc, avenues very shallow, Up. Sil., 4 species; Protaster (Forbes), disc small, arms long, extended, Upper (and Lower) Sil., 4 species. There appear to be no other forms yet described.

3. On the Physical Structure of the Earth; by Prof. HENNESSY, (Proc. Brit. Assoc.; Ath. No. 1504.)-After some preliminary observations as to the impossibility of accounting for the earth's figure, without supposing it to have been once a fused mass, the exterior of which has cooled into a solid crust, the process of solidification of the fluid was described. The influence of the connexion and circulation of the particles in a heterogeneous fluid was shown to be different from what would take place in a homogeneous fluid such as usually come under our notice. As the primitive fluid mass of the earth would consist of strata increasing in density from the surface towards the centre, its refrigeration would be that of a heterogeneous fluid, and the process of circulation would be less energetic in going from its surface towards its centre. Thus, the earth would ultimately consist of a fluid nucleus inclosed in a spheroidal shell. The increase in thickness of this shell would take place by the solidification of each of the surface strata of the nucleus in succession. If the matter composing the interior of the earth is subjected to the same physical laws as the material of the solid crust coming under our notice, the change of state in the fluid must be accompanied by a diminution of its volume. The contrary hypothesis has been hitherto always assumed in mathematical investigations relative to the form and structure of the earth. The erroneous supposition that the particles of the primitive fluid retained the same positions after the mass had advanced in the process of solidification as they had before the process commenced, had been tacitly or openly assumed in all such inquiries until it was formally rejected by the author, who proposed to assume for the fluid similar properties to those exhibited by the fusion and solidification of such portions of the solidified crust as are accessible to observation. The results to which the improved hypothesis has led show that it fundamentally affects the whole question, not only of the shape and internal structure of the earth, but also of the various actions and reactions taking place between the fluid nucleus and the solid shell. If the process of solidification took place without change of volume in the congelation of the fluid, the strata of the shell would possess the same forms as those of the primitive fluid, and their oblateness would diminish in going from the outer to the inner surface. If the fluid contracts in volume on passing to the solid state, the remaining fluid will tend to assume a more and more oblate figure after the formation of each stratum of the shell. The law of density of the nucleus will not be the same as that of the primitive fluid, but will vary more slowly, and the mass will thus tend towards a state of homogeneity as the radius of the nucleus diminishes by the gradual thickening of the shell. The surface of the nucleus, and consequently the inner surface of the shell, will thus tend to become more oblate after each successive stratum added to the shell by congelation from the nucleus.

This result, combined with another obtained by Mr. Hopkins, proves that so great pressure and friction exist at the surface of contact of the shell and nucleus as to cause both to rotate together nearly as one solid mass. Other grounds for believing in the existence of the great pressure exercised by the nucleus at the surface of the shell were adduced. If the density of the fluid strata were due to the pressures they support, and if the earth solidified without any change of state in the solidifying fluid, the pressure against the inner surface of the shell would be that due to the density of the surface stratum of the nucleus, and would, therefore, rapidly increase with the thickness of the shell. Contraction in volume of the fluid on entering the solid state would diminish this pressure, but yet it may continue to be very considerable, as the co-efficient of contraction would always approach towards unity. The phenomena of the solidification of lava and of volcanic bombs were referred to in illustration of these views, and their application was then shown to some of the greatest questions of geology. The relations of symmetry which the researches of M. Elie de Beaumont seem to establish between the great lines of elevation which traverse the surface of the earth appear to Prof. Hennessy far more simply and satisfactorily explained by the expansive tendency of the nucleus which produces the great pressure against the shell than by the collapse and subsidences of the latter. The direction of the forces which would tend to produce a rupture from the purely elevatory action of the pressure referred to would be far more favorable to symmetry than if the shell were undergoing a distortion of shape from collapsing inwards. The nearly spherical shape of the shell would also greatly increase its resistance to forces acting perpendicularly to its surface, so as to cause it to subside, while the action of elevatory forces would not be resisted in the same manner.

4. On the Great Pterygotus (Seraphim) of Scotland, and other Species; by Mr. J. W. SALTER, (Proc. Brit. Assoc., August, 1856; Ath. No. 1504.) This paper was in some measure a continuation of one published in the Quarterly Geological Journal for 1855, describing some new and large Crustacean forms from the uppermost Silurian rocks of the south of Scotland. They were described under the name of Himanthopterus, and were supposed to differ from the published fragments of the great Pterygotus by the lateral position of the large simple eyes. In the general shape of the body, however, the terminal joints aud tail, in the want of appendages to the abdomen, as well as in the form and number of the swimming feet, mandibles, maxillæ and antennæ, there was found to be on further examination the closest resemblance between Himanthopterus and the great Pterygotus. And the resemblance has been carried still further by the favorable collocation of all the known specimens from the Scotch collections which have furnished us with nearly all the portions, and also with the head, which we now find to be exactly like that of Himanthopterus, having lateral, not subcentral, eyes, as represented by other authors. The two genera are therefore identical, and the group, as now constituted, includes a number both of small and moderate-sized crustacea, along with some which were far larger than any living species, and which certainly attained a length of six or eight feet! The collections made by the Scotch geologists, in connection with other specimens SECOND SERIes, vol. xxii, NO. 66.—NOV., 1856.