I. Rock from a large quarry between North Malvern and West Malvern, disposed in horizontal tabular masses. Formerly broad slabs were obtained from hence, which were extensively used in the railway works; but these have been removed, and the rock which remains is loose, separating readily in nearly vertical lines. It is superficially stained with hydrated peroxide of iron. The iron in the interior of the rock is generally in a low state of oxidation, but some of it is in the form of anhydrous peroxide. There is much sulphate of baryta in this and in other quarries to the north of it. The rock, although easily fusible, is not altered where in contact with it: crystals of calc spar are found intermingled with it; and where the fissures are large, they are not filled by the sulphate of baryta, which is deposited in crystals on the opposite surfaces, leaving a vacant space of several inches between them. The sulphate of baryta cannot, therefore, have been injected into these fissures in a molten state after the consolidation of the rock. Baryta was not detected in the substance of the rock itself, which, when dissolved, after fusion with carbonate of soda, gave no precipitate with diluted sulphuric acid. This and the other rocks of which analyses are here given contain hydrofluoric acid, which cannot be completely eliminated by heat; after having been ignited until fusion of the rock had commenced, the presence of fluorine was still detected in it by fusion with bisulphate of potassa. This rock is uncrystallized, but it passes into syenite and mica schist.

II. Syenite, from the same place. The crystallization is imperfect, and some anhydrous peroxide of iron remains in an earthy state.

III. Amorphous rock from the same place, passing into mica schist. It differs from I. in having a smooth surface when fractured, and in being more of a slate colour than the latter. After being dried by evaporation at 212° Fahr., it gained 0.87 per cent. in weight by subsequent ignition, owing to the peroxidation of the iron.

IV. Hard mica schist, into which the above passes. The mean composition of these two agrees more nearly with the uncrystallized rock in the quarry (I.) than the composition of either of them taken separately. There may have been an

interchange of elements, some of the iron and magnesia in the mica of IV. having been derived from III., which retains a larger proportion of alumina, lime, and manganese.

V. Brownish grey rock, from the summit of the same quarry, uncrystallized, disposed in beds with vertical cleavage, similar to the rock below.

VI. Syenite from the same place, similar to II., but more fine grained.

VII. Greyish black rock, disposed in rectangular prisms, on the west slope of the North Hill, at a higher elevation than the preceding, and to the S.W. of them, quite uncrystallized, but passing into syenite.

VIII. Syenite, associated with the above; its chief constituent is hornblende. It is more perfectly crystallized than the syenites before mentioned (II. VI.) Thin veins of epidote are deposited in its crevices. The portion of the syenite of which an analysis is here given was taken from a part of the rock which did not contain any admixture of epidote.

Comparing I. and II., III. and IV., V. and VI., VII. and VIII., we find instances of the transition of rocks from the amorphous to the crystallized state, without any material change of composition; and as syenites and mica schists similar to these are found in other parts of the hill, we may thus trace them to their source, even where no amorphous rocks occur in their vicinity.

IX. Greyish black uncrystallized rock, forming rectangular prisms, south of the large quarry at North Malvern. It contains much hydrofluoric acid, and is very fusible. There is only a trace of soda.

X. Greyish black rock, forming a remarkable vein in the syenite north of the footpath from Great Malvern to West Malvern, overlooking the Westminster Arms. The vein dips slightly southward; it is about twelve feet long, and from a few inches to more than a foot deep; broken by a fault towards the north. Near the syenite it is marked by epidote; the interior is hard, compact, and uniform.

XI. A similar rock, taken from the middle of the railway tunnel under the South Hill.

In these two rocks, the ratio of the oxygen of the silica to

that of the bases is nearly 3:2. There is less silica in VII., and still less in IX. Yet these four rocks closely resemble each other in appearance. The rock containing least silica (IX.) has most water, and is probably most altered from its original composition; its alumina is reduced in quantity, and its soda nearly removed.

XII. Rock forming rectangular prisms, consisting of finegrained hornblende and epidote, from the west slope of the North Hill, near the summit, overlooking the hill road north of Elrington Cottages.

XII. Red rock, from a steep mound overlooking the south end of the road to Elrington Cottages. It is very hard, and spotted with epidote, and there are minute scales of gold mica. There is only a trace of hydrofluoric acid. All the iron is in a high state of oxidation. It passes into a coarse rock, containing much quartz; and in one place, towards the south, it is associated with a rock which runs in parallel bands, about four inches wide, and five inches apart, resembling metamorphic sandstone.

XIV. Rock found in rectangular prisms in a boss of trap near Fowlet Farm, of a greenish-brown colour, uncrystallized, with numerous cavities, which are partially lined with epidote. In the furnace, when allowed to cool rapidly, it fused into a black glass, like obsidian.

XV. Greyish black amorphous rock, from a trap boss near Bransil Castle. The cavities are filled with carbonate of lime.

XVI. Rock from another boss near Bransill Castle, in which are embedded velvet black portions, apparently of augite, but with no distinct crystallization.

XVII. Similar rock, from a boss of trap, in a field of black shale south of Fowlet Farm. It contains a little glassy felspar. The quantity of hydrofluoric acid is unusually large. XVIII. Grey trap rock, from a boss near Rowick, containing magnetic oxide of iron.

XIX. Trap rock from the south-west base of the Ragged Stone Hill. The iron in the part of the rock which is soluble in hydrochloric acid is in a low state of oxidation; the insoluble portion contains a little peroxide.

XX. Trap from the north-west side of the West Ragged Stone. The portion soluble in hydrochloric acid contained magnetic oxide and protoxide of iron; the insoluble portion, peroxide.

XXI. Rock from the same place, after passing over the sandstones, and immediately before arriving at the trap of the hill. It contains black granules, like gunpowder. There are in it hydrofluoric acid and a little potass, but no soda; and it seems to consist of minutely divided hornblende and quartz.

On Nerve Force. By H. F. Baxter. (Continued from Vol. XII. p. 39.)

In a former paper, published in the "Edinburgh New Philosophical Journal,"* I endeavoured to ascertain whether any manifestation of current force could be obtained in nerves during nerve action. My experiments led to a negative conclusion; neither could I obtain any direct evidence of an increase in the nerve current during nerve action; but whether any evidence of a conversion, as it were, of the electric force of the nerve into nerve force during nerve action existed, remained as an open question. My object, however, on the present occasion, will be to inquire whether we can obtain any evidence of an inductive effect of one nerve upon another nerve during nerve action.

Claude Bernardt says, "Du Bois Raymond has proved that in electrifying the nerves, an electro-tonic state is produced, which does not act upon the muscles, but upon the nerves which lie in the vicinity; they are liable, in fact, to receive a part of the superabundant electricity condensed in the neighbouring trunk. Let it be supposed, for instance, that a current passes through a nerve, which lies in contact with another divided nerve, contractions will appear in the muscle connected with this latter branch, although no direct impulse has been conveyed to it; the proximity of another nerve,

* New Series, July 1860. I may also refer to my Essay on Organic Polarity, published by Churchill.

† Medical Times and Gazette, Angust 17, 1861.

stongly impregnated with the electric fluid being sufficient to create a participation in its effects."

M. Chauveau,* in some valuable and interesting papers, has shown that when the nerves of two separate limbs are placed parallel and in contact with each other, upon stimulating one of them the limb of the other would contract. The effects varied according as the electric current traversed the nerve, and it was necessary to employ electricity.

Having failed in my former experiments in obtaining any evidence of an increase in the electric condition of the nerve after being submitted to electrical action, the opinion expressed by Claude Bernard, that "one nerve received a part of the superabundant electricity condensed in the neighbouring trunk," does not appear to me to be supported by sufficient evidence, but would rather confirm the notion that some inductive effect might then be produced.

In the following experiments the nerve of the limb primarily stimulated will be designated by the letter a, and the nerve of the other limb,† in which any inductive effect may be supposed to take place, such as would be indicated by muscular contraction, will be designated by the letter b.

M. Chauveau dissected out the sciatic nerves of a frog, removed the thigh, leaving the nerve connected with the leg only; then placing the nerves parallel to each other and in contact, stimulating a portion of the nerve a by means of a current from a small voltaic circle between the leg and the part in contact with b, an effect was produced on the nerve b, as indicated by muscular contraction of that limb. The effects varied according as the nerves were placed in contact with each other, whether in the same direction or reversed, and according to the direction of the current, whether ascending or descending. The distance between the stimulated portion of

* Journal de Physiologie, Juillet et Octobre 1859, Janvier et Avril 1860. †The limb b has been usually designated as the rheoscopic or galvanoscopic limb. I shall avoid using either of these terms on the present occasion, inasmuch as my object is not to ascertain whether any electrical effect is observed, but whether any effect like nerve induction takes place, just as we obtain an inductive effect when a closed metallic circle is placed in the neighbourhood of another closed circle traversed by an electric current.