Penny Blood: Serial Sensation and Working-Class Entertainment — page 21: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

4 ON UNDERGROUND TEMPERATURE. [CH. I. upon as chiefly a manifestation of the generally diffused heat of the interior, by the escape of which the contraction in volume is produced. Volcanic action, Mr Mallet tells us, is caused by this:contraction manifesting itself locally and paroxysmally. In order to decide what theory best accounts for the phe- nomena, it is obvious that the first step is to make sure of the facts themselves, In other words—What is the law regulating this increase of heat? At what rate does the temperature augment? This might be supposed to be a point easily settled. It might be supposed that nothing would be easier than to insert thermometers into the rock at different depths in a mine, and to read off their indications; or to lower them into a bore- hole for the same purpose. But there are many difficulties to be overcome, and a host of disturbing causes present. The rock, or the face of the coal in a mine, is affected by the tem- perature of the air. The air is warmed by the presence of men and horses; it is cooled by the ventilation carefully kept up. Hence the surface of the working is not at the true temperature of the rock. The result of careful experiments made by Sir G. Elliot showed that when thermometers were inserted in the coal in a long-wall working, at distances of 3, 6, and 12 feet from the face, no alteration could be detected in the indications given beyond 3 feet from the face of the coal; and his observa- tions were accordingly taken at 4 feet. It is evident, as will be seen by what will be said hereafter, that the necessary distance must be governed by the difference between the temperature of the ventilating air and of the seam, and that the greater this difference the farther it would be necessary to bore into the coal to obtain an estimate of its true temperature. If it be attempted to ascertain the law of increase by means of an Artesian bore-hole, there are here also disturbing causes present. The action of the tool warms the rock by mechanical means, the friction or pounding action developing considerable heat. Hence while the work is in progress no reliable observations can be taken, except during intervals of suspension, and then it ap- pears—as will be.seen further on—that the interval needs to consist of weeks rather than of days. When the work is com- pleted, and the bore stands nearly full of water, it 1s the tem- COMICOOOLKS @ (CO)