rate. No, it is said, the hypothesis of Davy does not consider these bodies as subhydro-chlorates. They are composed of the chloride of copper or lead, combined with the oxide of the same metal and with water, so that for one atom of chloride there are three atoms of oxide and four of water, a composition which agrees perfectly with the laws of chemical proportions. But this is a mistake. It is conformable, indeed, to the atomic theory of Dalton, which pays no attention to the relation of the oxygen of the different oxides combined; but it is contrary to the law above stated; for it supposes that the oxygen of the oxide is 88.6, and that of the water 1178; that is, that the former is only three-fourths of the latter. I do not know whether the new hypothesis admits still other explanations; but it is obvious that the two explanations given here are contrary to the law which determines the respective quantities of bodies that combine. Therefore either that law or the hypothesis is incorrect. Sir H. Davy, in speaking of my objections to his hypo thesis, says, "I cannot regard these arguments as possessing any weight; "" and there is no general canon with respect to the mul tiples of the proportions in which different bodies combine." I do not think that this manner of refuting is admissible in the sciences. This celebrated chemist has taken advantage of his great superiority, and has predisposed the reader to believe that six years of labour on my part to find and to establish by numerous experiments the law, which he says does not exist, have been lost without fruit. I suppose, however, that he will one day do me the justice to take the trouble to prove by experiment that I have deceived myself if he finds that I am in the wrong.

ARTICLE IX.

An Essay on the Shapes, Dimensions, and Positions of the Spaces in the Earth which are called Rents, and the Arrangement of the Matter in them with the Definition and Cause of Stratification. By Mr. John B. Longmire.

1. Additional Remarks on the Positions of the Strata near BendedTabular Rents.

I HAVE before laid it down as a general rule that the distance which the strata are asunder on opposite sides of bended-tabular rents is owing to a bending in the strata, which commences at the lowest extremities, increases to the middles, then decreases to, and ends at, the highest extremities of these rents. But, although this

is the general mode, and one that is subject to some modifications, there is another mode by which this difference of level is produced.

Miners often find the strata, any distance from a foot to more than 40 fathoms asunder, in point of altitude, on opposite sides of bended-tabular rents, in places where these strata are not bent; but straight, as the stratum a b c d, Plate XXXVIII, fig. 1, and the stratum c, along with the strata B A, fig. 2, are represented. In the first mode, the distances which the strata are asunder, on opposite sides of these rents, are obtained by the bending of the strata, and always continue, and sometimes increase, during many temporary suspensions of this bending; but in the second mode, it takes place without any bending of the strata.

I will give one example to illustrate each mode. Let fig. 1 be representative of the first mode. The stratum ad is horizontal, notwithstanding the part ab is the distance b c below the part c d. Above this stratum, at the rent A, the strata are straight for a certain distance, and then they are bent; and below this stratum they are also bent, at first slightly, but with a gradually increasing ratio, that reaches its maximum at the stratum kn; whose two parts kl and mn are the distance m l asunder, which is equal to the distance fg, and to the distance bc, and which is acquired by the bending of the part m n above the line n. The strata close to the side pg c at this part of the rent are thicker than close to the side lfb: they are also thicker at mp than at qn, and that additional thickness throughout the whole of the rent, below the stratum kn, gave rise to the bending of the part m n of that stratum, in the manner which has been shown in my first communication on rents; but the strata above the stratum m n where close to the side m c of the rent, though thicker than the opposite strata on the side b, are not so thick as they are at the line n d; in consequence, the bending, as seen at m n, gradually decreases upwards till it ceases. Let us take, by way of illustration, the effect on the stratum c h, of this alteration in the thickness of the strata: as much as the strata which are situated between the strata kn and ch are thicker at the linen h than at ke, so much is the distance n h greater than the distance ke, (say by the distance k o,) and so much is the stratum g h bent less than the stratum m n, say by the distance ir. The bending of the strata above the stratum c h also diminishes upwards, from the same cause, till it ceases at the stratum a d, which is straight. At first sight the position of the stratum a d, considering how much one part is higher than the other, appears to be irreconcileable with that arrangement which I have considered the general one; but when its connexion with that of the strata below is traced as we have now done, its difference from that which is the common one is easily accounted for. In fact, the arrangement of the elementary matters in this part is such, that the strata have contracted less, instead of more, at the line nd than close to the side m c of the rent; and by doing so have gradually given the straight, instead of

the bended position to the strata of this part: while these strata close to the rent have contracted, as usual, less on the under side pc than on the upper side lb. Hence also the distance between the straight strata on opposite sides of this rent is equal to that between similar parts of the bent strata.

An example of the second mode is that which follows. Sometimes the strata near bended-tabular rents are all, or nearly all, straight, notwithstanding they are situated at different levels on opposite sides. Thus the strata A B C, fig. 2, and those which lie between them, are straight on both sides of the rents DE; but the parts of the strata bf k and è in are higher on the under sides than the parts cg and d h m on the upper sides of these rents. The strata in this figure, as well as those near all rents of this shape, are thicker on the upper than on the under sides; and by this greater thickness the stratum A is higher at be than at c d, the stratum B at fi than at gh, and the stratum C at k n than at l m. Now, as has been before shown, this difference in the thickness of the strata is a consequence of the unequal contraction of the stratified matter; that is to say, the strata have contracted more near the upper sides than near the under sides of these rents. But although they have contracted with different ratios on different sides, yet in the example before us the ratio on any one side has been uniformly the same throughout the strata, instead of being, as in general, the least near the rents, and the greatest at given distances from them. In consequence, then, of this uniformity in the ratio of contraction of the strata, when taken on one side only, they are straight on both sides of some rents, although they are situated at different levels on opposite sides of such rents.

It may be proper to remark here that, though the strata are straight, and higher on one side of a rent than on the other, when seen in a cross section, as in fig. 2; yet when a view is taken at right angles to this section, or when a person faces the rent, every stratum then separates at one horizontal extremity into two parts, one inclining very gently upwards, and the other downwards, till opposite the middle of the rent; then the higher part dips downwards, and the lower part rises upwards, till they meet again at the other horizontal extremity of the rent.

2. Observations on the Upper Extremities of large Bended-Tabular Rents.

The upper extremities of some rents are altogether situated in the solid rock, and at considerable distances below the surface. Many large rents extend downwards from the surface of the solid rock, or that of the solid strata, to great depths; but some of them reach above the solid, through the alluvial matter, to within a few inches of the earth's surface.

Some of the rents which reach nearly to the surface are precisely of the same dimensions in the alluvial clay, as in the solid rock