Penny Blood: Serial Sensation and Working-Class Entertainment — page 30: what you’re looking at

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

cH.1.] ON UNDERGROUND TEMPERATURE. 13 mnade with the geo-thermometer can be depended upon as having given the true temperature of the rock in mass, two questions present themselves, First, could the water enclosed between the disks assume eventually the temperature of the rock mass, if the instrument were left down long enough? And, secondly, if it could do so, was it in fact left down long enough ? It appears that this result could be only partially at- tained, however long it were left in the bore-hole. The convection currents in the water would affect the tempera- ture of the column at the upper and under surfaces of the enclosing disks of the instrument. And even if the disks were purposely made of such badly-conducting material as to prevent any temperature effect from the currents being carried ‘through the disks, still such effect would be conducted round the edges of the disks, through the substance of the rock itself; consequently, however long the instrument might have been allowed to remain down, the temperature of the water enclosed between its disks would have been to some extent affected by the convection currents; and their tendency 1m the lower parts of the column would be to reduce the temperature, and diminish the rate of increase. A method of obviating this source of error is mentioned in the British Association Report, already referred to, as having been lately suggested by Sir Wm. Thomson. It consists in using a series of india-rubber disks placed at considerable dis- tances apart. Putting the above-discussed source of error aside, we come to our second enquiry, whether the geo-thermometer was left down long enough for the water between its disks to assume the temperature of the rock mass’? Let us, then, consider the conditions of the system before the geo-thermometer is introduced. We have a very long vertical column of water 1 Tt appears that at the depth of 1100 feet an observation of ten hours duration gave the same result as one of nineteen hours; whence it was con- cluded that ten was long enough. But considering the great thermal capacity of water, and the small changes which, except just at first, might be expected in the rock, as well as the difficulty of the operation, this trial can hardly be held conclusive against the probability of a further increase of temperature, if the geo-thermometer had remained down longer. COLA @ NOO (CO) =h