14 
UNDERGROUND TEMPERATURE. 
Observations have also been made in deep bore-holes, but these 
offer two objections, viz.: convection, and the time it takes to raise 
the thermometer. The latter difficulty, however, has, to a great 
extent, been overcome by the construction of slow-acting thermom- 
eters, but the former has not as yet been satisfactorily dealt with. 
In the Quarterly Journal of Science, for January, 1868, Mr. Hull, 
F.G.S., points out the necessity of observations at low depths, and 
suggests the idea of starting a bore-hole within the workings of a 
mine. I need hardly say, that if such could be accomplished, 
most reliable results could be obtained, but such opportunities do 
not often present themselves. A few observations have been made 
within the workings of mines, but objection has been taken on the 
ground, that the results would be affected by the air-currents, by 
the heat of the lamps, by the bodies of the colliers and horses. 
Doubtless where the thermometers cannot be isolated from these 
influences, little reliance could be placed in the results. In mines 
where explosive gas is generated, it might be impossible to isolate 
the thermometer from a brisk air-current, but, as in the case of our 
own coalfields, where the majority of coal-seams do not yield 
explosive gas, this difficulty may often be got over. 
Last year (1878) Prof. Everitt sent me one of Negretti & Zambra’s 
patent mining thermometers, for observations in the workings of 
the Kingswood Collieries, near this city. The way in which I 
proceeded was as follows : — observations were made only in new 
ground, and the thermometer was inserted on the day on which 
the strata were exposed : for this reason, cross measure branches 
and advanced levels were selected as the places for operation. 
The thermometer was placed in a hole 2 feet deep, and the mouth 
was tightly closed with clay rolled in the form of a plug. 
The following is the method of which I was able to avail myself : 
The branch A is driven in the solid rock ; the air enters as 
indicated by the arrows, and returns through the trunks B. If, 
therefore, the mouth of the trunks is removed a few feet back 
