taic series, or a wire subjected to electro or magneto-dynamic induction. In the latter instances the shock is reiterated so rapidly as to appear more enduring, while in the former, it is more startling and producible at an infinitely greater distance.

78. Agreeably to Faraday's researches (1485 to 1543), there is reason to suppose that in frictional spark discharges, the consequent shock, light, and other peculiarities, are in part owing to waves of ethereo-ponderable polarization, indirectly produced in the intervening gaseous matter. (71.)

Of Ethereo-ponderable Deflagration.

79. It is well known, that between two pieces of charcoal attached, one to the negative, the other to the positive pole of a numerous and well excited voltaic series, an arch of flame may be produced by moving them apart after contact. This phenomenon evidently depends upon the volatilization of the ponderable matter concerned; since it cannot be produced before the carbon has been volatilized by contact, nor by any body besides charcoal, this being the only conductor which is sufficiently infusible, and yet duly volatilizable. Metals, similarly treated, fuse at the point of contact and cohere. On separation, after touching, a single spark ensues; which, without repetition of contact, cannot be reproduced. Hence, it may be inferred, that the carbonaceous vapor is indispensable to this process, as a medium for the ethereo-ponderable polarizing waves, being soon consumed by the surrounding atmospheric oxygen. The excrescence upon the negative charcoal, observed by Silliman, together with the opposite appearance on the positive charcoal, may be owing to the lesser affinity for oxygen on the negative side.*

80. There may be some resemblance imagined between this luminous discharge between the poles, and that which has already been designated as diruptive (69); but this flaming arch discharge does not break through the air, it only usurps its place. gradually, and then sustains this usurpation. It differs from the other as to its cause, so far as galvanic reaction differs from friction; moreover, it requires a volatilizable, as well as a polarizable ponderable conducting substance to enable its appropriate undulations to meet at a mean distance from the solid polar terminations, whence they respectively proceed.

81. The most appropriate designation of the phenomenon under consideration, is that of ethereo-ponderable undulatory deflagration. Under this head, we not only place the flaming arch, but likewise the active ignition and dissipation of fine wire or leaf metal, or when attached to one pole, and made barely to touch the other.

* American Journal of Science, vol. x, p. 121, 1826.

82. In one of Faraday's experiments, a circuit was completed by subjecting platinum points, severally proceeding from the poles of a voltaic series, while very near to each other, to the flame of a spirit lamp. This was ascribed by him to the rarefaction of the air, but ought, as I think, to be attributed to the polarizable ethereo-ponderable matter of the flame, performing the same office as the volatilized carbon in the flaming arch, between charcoal points, to which reference has been made.

Summary. From the facts and reasoning which have been above stated, it is presumed that the following deductions may be considered as highly probable, if not altogether susceptible of demonstration.

The theories of Franklin, Dufay and Ampère, are irreconcilable with the premises on which they are founded, and with facts on all sides admitted.

A charge of frictional electricity, or that species of electric excitement which is produced by friction, is not due to any accumulation, nor to any deficiency either of one or of two fluids, but to the opposite polarities induced in imponderable ethereal matter existing throughout space however otherwise void, and likewise condensed more or less within ponderable bodies, so as to enter into combination with their particles, forming atoms which may be designated as ethereo-ponderable.

Frictional charges of electricity seek the surfaces of bodies to which they may be imparted, without sensibly affecting the ethereo-ponderable matter of which they consist.

When surfaces thus oppositely charged, or, in other words, having about them oppositely polarized ethereal atmospheres, are made to communicate, no current takes place, nor any transfer of the polarized matter: yet any conductor touching both atmospheres, furnishes a channel through which the opposite polarities are reciprocally neutralized by being communicated wave-like to an intermediate point.

Galvano-electric discharges are likewise effected by waves of opposite polarization, without any flow of matter meriting to be called a current.

But such waves are not propagated superficially through the purely ethereal medium; they occur in masses formed both of the ethereal and ponderable matter. If the generation of frictional electricity, sufficient to influence the gold leaf electrometer, indicate that there are some purely ethereal waves caused by the galvano-electric reaction, such waves arise from the inductive influence of those created in the ethereo-ponderable matter.

When the intensity of a frictional discharge is increased beyond a certain point, the wire remaining the same, its powers become enfeebled or destroyed by ignition, and ultimately deflagration:

if the diameter of the wire be increased, the surface, proportionally augmented, enables more of the ethereal waves to pass superficially, producing proportionally less ethereo-ponderable undulation.

Magnetism, when stationary, as in magnetic needles and other permanent magnets, appears to be owing to an enduring polarization of the ethereo-ponderable atoms, like that transiently produ ced by a galvanic discharge. (Note, page 230, vol. v, and paragraph 68.)

The magnetism transiently exhibited by a galvanized wire, is due to oppositely polarizing impulses, severally proceeding wavelike to an intermediate part of the circuit where reciprocal neutralization ensues.

When magnetism is produced by a frictional discharge operating upon a conducting wire, it must be deemed a secondary effect, arising from the polarizing influence of the ethereal waves upon the ethereo-ponderable atoms of the wire.

Such waves pass superficially in preference; but when the wire is comparatively small, the reaction between the waves and ethereo-ponderable atoms becomes sufficiently powerful to polarize them, and thus render them competent, for an extremely minute period of time, to produce all the affections of a galvanoelectric current, whether of ignition, of electrolysis or magnetization. Thus, as the ethereo-ponderable waves produce such as are purely ethereal, so purely ethereal waves may produce such as are ethereo-ponderable.

The polarization of hair upon electrified scalps is supposed to be due to a superficial association with the surrounding polarized ethereal atoms, while that of iron filings, by a magnet or galvanized wire, is conceived to arise from the influence of polarized ethereo-ponderable atoms, consisting of ethereal and ponderable matter in a state of combination.

Faradian discharges are as truly the effects of ethereo-ponderable polarization, as those from an electrified conductor, or coated surfaces of glass, are due to static ethereal polarization (39, 40, 41); last paragraph, note, p. 346.

It is well known that if a rod of iron be included in a coil of coated copper wire, on making the coil the medium of a voltaic discharge, the wire is magnetized. Agreeably to a communication from Joule, in the L. and E. Phil. Mag. and Jour. for Feb., 1847, the bar is at the same time lengthened, without any augmentation of bulk; so that its other dimensions must be lessened in proportion to the elongation.

All these facts tend to prove that a change in the relative position of the constituent ethereo-ponderable atoms of iron, accompanies its magnetization, either as an immediate cause, or as a collateral effect.

ART. VI.—Upon a peculiar kind of Isomorphism that plays an important part in the Mineral Kingdom; by Professor SCHEERER Of Christiania.*

(Continued from vol. v, p. 389)

THE query might be started, how it is then, since aspasiolite and cordierite are so closely associated, that serpentine is not accompanied by olivine? This circumstance, which, it must be confessed, does appear paradoxical, I purpose to enter upon towards the close of this paper.

Upon the theory based on the above mentioned relations of cordierite and aspasiolite, being thus borne out by the precisely similar relations subsisting between olivine and serpentine, the probability was increased, that the part played by this species of isomorphism in the mineral kingdom was not one restrained within very narrow limits. And this opinion has taken a development more extended than I even imagined it might be susceptible of, as my investigations have been carried out. In the sequel I purpose touching upon the principal minerals concerned in this inquiry, and to develope their suitable formulæ, upon the supposition that their water may be treated as a basic constituent, capable of replacing in the ratio that has been stated, (viz. three atoms to one atom,) the magnesia, and consequently all the other bases isomorphous therewith, as for instance, protoxyd of iron, protoxyd of manganese, and so forth.

In order to express as simply as possible that in a member of a formula R, a portion of the 1: 1 atomic bases is replaced by more or less water, I have in these cases invariably made use of the sign (R), as was already the case with regard to serpentine. The formula of aspasiolite would therefore, upon this principle, be (R) Si +3R Si. Prior to proceeding to the results of my calculations, let me however very briefly further elucidate the kind of isomorphism forming the subject of our investigations, in a chemical point of view. From the composition of aspasiolite and of serpentine, it follows that in the former, one equivalent R (one-third of the entire 1: 1 atomic bases contained in cordierite) is not replaced by water exactly. It is likewise clear that, as in serpentine the amount of water ranges between 12, 27 and 21 per cent., it does not observe any definite atomic proportion relative to the portion of the 1:1 atomic bases not made good by water. This is to be explained as follows, in a very simple manner, strictly upon the principle of an isomorphic substitution.

From Poggendorff's Annalen, vol. lxviii, p. 319; translated for this Journal by Mr. W. G. LETTSOM.

SECOND SERIES, Vol. VI, No. 16-July, 1848.

8

From the circumstance of three equivalents of water being able to replace isomorphically one equivalent of magnesia, it directly follows that combinations such as Mg3 Si, Mg2 Si + 3, and Mg Si+6H, must, of necessity, possess the same crystalline form. Such combinations therefore, under this common form, can occur mixed together in every possible proportion, and thereby explain the occurrence of non-definite proportions in the respective amounts of water and of magnesia, not only as met with in aspasiolite and in serpentine, but also, as may be deduced from the sequel, in a very considerable number of other minerals containing water.

I. SILICATES.

A. Silicates of magnesia and other bases isomorphous therewith, (minerals allied to serpentine.)

1. Gymnite. (Thomson.)

=20.86

20.56. Formula deducible

Oxygen ratio, Si: (R) 20.86: 20:56.

therefrom, (R) Si.

(R) in this mineral = 36.00 Mg, 21-60 H, 0·80 Ca. In addition thereto, Thomson found in gymnite 1·16 ferriferous alumina. Deducting this as a silicate, the oxygen ratio given above becomes modified to 20-36: 20.56, approximating therefore even

yet closer to 1: 1.

(B) = 40·0 Mg, 200. The siliceous hydrate of alumina from Baltimore has a similar composition, according to Allan. 3. Villarsite. (Dufrènoy.)

20-47 21-37.

(R) from two analyses 45-33-47-37 Mg, 4-30-3.59 Fe, 2.86 −2.42 Mn, 0·54–0·53 Ča, 0·46 K, 5·80 H.

4. Dermatine. (Ficinus.)

19.74 18.79. (R)3 Si.

(Ŕ) in two analyses = 23·70-19.33 Mg, 11.33–14:00 Fe, 2·25 -1.17 Mn, 0.83-1.83 Ca, 0·50-1.33 Na, 25-20-22 H, and in addi

tion thereto, 0.42-0-83 Al; deducting this latter as silicate, the oxygen ratio becomes altered to 19-44: 18·79.

5. Chrysotile. (Metaxite, Delesse.)