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thoroughly separated by washing. If we then consider the deficiency of the weight, as water of crystallization, the salt is composed of

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If we suppose an atom of oxide of nickel to be = 37, the composition of the salt will be;

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These proportions, it will be observed, do not differ much from those stated by M. Berzelius and Mr. Brande.

One hundred grains of the square prisms of sulphate of nickel were treated as above described: the mean of the experiments gave 88.65 of sulphate of barytes, equivalent to 30 of sulphuric acid; the oxide of nickel amounted to 26-2 grains. This salt, therefore, consists of

Sulphuric acid.
Oxide of nickel

Water...

30.0

26.2

43.8

100.0

The excess of sulphuric acid contained in the square prisms, amounting to less than 2 per cent. cannot, I think, be considered as existing in a state of combination, but merely of mixture; and as such, we should not expect that it would influence the crystalline form of the salt.

It will be proper to state, that the result of Mr. Cooper's analysis agreed very nearly with my own, and that I confirmed the accuracy of his observations with respect to the different effects produced on these salts by exposure to the air; the rhombic prisms lost one atom of water, while 100 grains of the square prisms suffered a diminution of only one-tenth of a grain in weight.

Mr. Cooper informs me that he has analyzed the sulphate of nickel and potash, and finds that it is composed of

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ARTICLE XI.

Substance of certain Papers on the Temperature of Mines, published in the Transactions of the Royal Geological Society of Cornwall.

WHEN reviewing the second volume of the Transactions of the Cornish Geological Society, Annals, N. S. v. 295, we mentioned that a memoir would shortly appear in our journal, containing a full account of the facts detailed in four papers on the temperature of mines published in that volume. Various circumstances have interfered to prevent the completion of the memoir, and as the period of its appearance is now uncertain, we purpose, in the present article, to give the substance of three of the papers alluded to, that of the fourth, by Mr. Moyle, having already been detailed by its author in the Annals for January last, p. 43.

I. The first paper (Trans. GSC. ii. 14-18) is by R. W. Fox, Esq. Member of the Society.

My attention, he says, having been called to this subject in 1815, I instituted inquiries, and caused some experiments to be made in the mines of Huel Abraham, Dolcoath, Cook's Kitchen, Tincroft, and in the United Mines. The information I have thus acquired I have endeavoured to communicate in the accompanying scale, which exhibits at one view, the results which have been obtained in each of those mines.

The temperature in Cook's Kitchen and Tincroft, it may be remarked, was inferior to that in the other mines at corresponding depths; owing, I presume, to the bottom levels of the two former having been for a considerable time filled with water, accumulated, without doubt, partly from above; by which means, the temperature, not only of the water, but also of the air, in these mines, must have been affected. In the United Mines also, there was some water when the observations were made; but it remained too short a time, I apprehend, materially to affect the general temperature of the mine. Dolcoath and Huel Abraham were clear of water to the bottom; and it will be observed that the temperature in the corresponding levels of these mines differed very little, and, with a few trifling exceptions (which probably arose from local causes), the heat progressively increased, even to the greatest depths to which they have been hitherto explored.

From Mr. Fox's engraved scale, as mentioned above, the table on the following page has been drawn up, with a slight alteration in its arrangement to suit that mode of giving it :—a signifies the temperature of the air, w that of the water.

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II. The table which accompanies Mr. Fox's second paper (Trans. GSC. ii. 19-28), contains a general view of the heat observed in, or near, the metallic veins, in different mines.

I had made a second table, he remarks, containing the results of several experiments on the temperature of cross levels, and shafts, in some of the same mines, at a distance from any metallic veins; but as its contents are too various, and extensive, to be comprised in a printed sheet, I will merely mention a few of the particulars.

In Dolcoath, at the depth of 130 fathoms, where the temperature of the earth in the vein was 63°; its temperature in a cross level, at the distance of 60 fathoms from the vein, was 62°.

In the United Mines, at the depth of 160 fathoms, the temperature of the earth in the vein, was 75°; but in a cross level, south of the vein, only 69°.

In the same mines, the temperature of the water in the vein at 140 fathoms deep, was 67°; and that of the earth, 9 fathoms north of the vein, was exactly the same.

In Ting-tang, at 80 fathoms deep, the temperature of the earth in the vein was 64°; and at the depth of 110 fathoms, it was 68°; whilst in a cross level, 90 fathoms deep, and 30 fathoms distant from the vein, it was 64°.

In Huel Squire, at the depth of 110 fathoms, the temperature of the air near the vein was 72°; but in a cross level, at some distance, it was 69°.

In Treskerby, at 120 fathoms deep, the temperature of the air near the vein was 72°; but at some distance, in a cross level, 66°.

In Chacewater, the temperature of the earth in the vein at 100 fathoms deep was 82°; and that of the air at some distance north of it, 79°.

These instances, which are selected from a great number, the result of which is very similar, will suffice to show, that the temperature, at a distance from the metallic veins, and at the same depths, is, on an average, nearly three degrees below that of the veins, as given in the printed table.

In many of the observations referred to in the tables, the bulb of the thermometer was buried in the veins, or rock, to the depth of at least six or eight inches, and was filled round with earth, &c. so as to prevent the free admission of air.

If we take the mean temperature of the surface of the earth in this latitude at 53°, as given in Prof. Mayer's Tables; the mean of the accompanying table shows an increase of a little more than 6° of Fahr. for every 50 fathoms, or 300 feet in depth. As my second table gave a less ratio, perhaps we shall not much err, if we suppose an augmentation of one degree of heat for every 10 or 12 fathoms in depth, at least in this part of our island. It is however difficult to determine satisfactorily the true ratio of the increase of temperature, as it is evident that there exist many

local and accidental causes which operate in our mines, and affect their temperature. The lighted candles, and the blasting of the rocks, have doubtless some influence in augmenting the heat; and the presence of the workmen must also have the same tendency, although probably in a small degree at the bottom of deep mines, where the temperature so nearly approaches to that of the human body; moreover, the warm vapour, and air, which always arise from the bottom of mines, must raise the temperature of the upper levels in a greater or less degree, according to their relative situations. On the other hand, the currents of air which descend through some of the shafts, or are forced through the air-pipes for the supply of the miners, and likewise the water which finds its way through the strata and veins from more elevated situations, doubtless tend, in a considerable degree, to diminish the heat in the deeper levels.

How far these opposite causes may counterbalance each other, it is not easy to ascertain; but if duly considered, they will greatly reconcile the want of complete accordance in the results noted in the tables; and it is evident, that observations made on the temperature at the bottom of mines, are most to be confided in, not only for the foregoing reasons, but also because of the proximity of this part to the unbroken ground. There are some cases in which it cannot be supposed that the high temperature observed can be occasioned by any accidental circumstance. At the bottom of Dolcoath mine, for instance, there is a large stream of water issuing from one of the veins at 82° of Fahr. while the air near the same place is generally one or two degrees lower-this is only one example amongst many of the same kind. The most striking one I have heard of, was reported to me by Capt. Hosken :-An accident having happened to a steam engine at the United Mines, the water increased so much as to fill the levels marked in the table 190 and 200 fathoms, under the surface; and thus it continued for two days. Immediately after it had been pumped out, and before the miners had begun to work in those levels, he ascertained the temperature of the ground in the upper one to be 8740, and in the lower one to be 88°. On renewing his observations some days after the men had resumed their work in these places, the heat had rather diminished than otherwise.

It is worthy of notice, that the principal part of the work is not always carried on in the deepest part of the mines: on the contrary, there are often more workmen employed at twenty or thirty fathoms above the lowest part, than in the deepest level. If therefore the increase in the temperature were wholly the effect of adventitious causes, that increase would be greatest where those causes had their largest operation; but the facts which I have detailed in the table, prove that, however various may be the operation of accidental circumstances in different parts of the mines, the temperature invariably increases with the depth.

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