Mr Bald on the Fires that take place in Collieries. 119 



and at last came in contact with the burning coals and red hot- 

 rocks. This produced a very unlpoked for phenomenon ; for 

 the steam, of very high temperature, rushed with impetuosity 

 directly to the pit b, where it rapidly ascended, and at its mouth 

 formed a dense cloudof steam which rose to a great height, and was 

 seen at many miles distant. This steam by degrees heated the direct 

 air-course, which, at last, became as a heated steam-tube ; and 

 not only the steam, but free and disengaged caloric, issued from 

 the mouth of the pit, pure and invisible at the surface, the steam 

 only becoming visible after coming in contact with the atmos- 

 pheric air, at some distance from the pit mouth : so hot were 

 the steam and air that they singed the hairs on the back of the 

 workmen's hands ; — the consequence of this was, that this sud- 

 den transit of the steam and caloric encreased the fury of the 

 burning mass, by drawing to it a great quantity of atmospheric 

 air, from the dip part of the colUery ; and for some days the 

 fire encreased in fierceness. 



In order to try the temperature of the steam and caloric, J 

 hung down the pit 6, a thermometer, of Fahrenheit's scale, the 

 highest range of which was 232° ; and upon drawing it up, I was 

 astonished to find the mercury up at the top of the tube ; so that 

 the absolute temperature I could not ascertain. This happened 

 upon the 8th day of March 1828, I requested Mr Dewar,the ma- 

 nager, to try the temperature frequently ; and, upon the 12th of 

 that month, the temperature had sunk to the boiling point 212°. 

 The water now began to operate effectually, and we had the 

 satisfaction of finding, upon the 14th of the month, that the tem- 

 perature was reduced to 165». These trials were made in an 

 opening of the pit-covering, of about eight inches square. 

 The temperature gradually decreased to the 7th of May *, when 

 it was 85°. We then threw off the covering from the pit, which 

 gave a free issue to the steam, conceiving that the cooling pro- 

 cess would go on more expeditiously, but to our great surprise 

 the temperature encreased rapidly to 108°, and on the 13th it 

 rose to 109°. On the 14th, we again covered the pit, and left 

 a small opening as before, when the temperature was suddenly 

 reduced to 97°. It has since that day progressively gone down- 



• I have added the results down to the 2l8t of May, when this paper went 

 to press. 



