THE LIMITS OF OUR COAL SUPPLY. 199 



elusions of a physician on such a subject, but I do so 

 nevertheless, as the data required are simple practical facts 

 such as are better obtained by furnace-working than by 

 sick-room experience. 



During the hottest days of the summer of 1868 I was 

 engaged in making some experiments in the re-heating 

 furnaces at Sir John Brown & Co. 's works, Sheffield, and 

 carried a thermometer about with me which I suspended 

 in various places where the men were working. At the 

 place where I was chiefly engaged (a corner between two 

 sets of furnaces), the thermometer, suspended in a position 

 where it was not affected by direct radiations from the 

 open furnaces, stood at 120 while the furnace doors were 

 shut. The radiant heat to which the men themselves were 

 exposed while making their greatest efforts in placing and 

 removing the piles was far higher than this, but I cannot 

 state it, not having placed the thermometer in the position 

 of the men. In one of the Bessemer pits the thermometer 

 reached 140, and men worked there at a kind of labor 

 demanding great muscular effort. It is true that during 

 this same week the puddlers were compelled to leave their 

 work; but the tremendous amount of concentrated exer- 

 tion demanded of the puddler in front of a furnace, which, 

 during the time of removing the balls, radiates a degree of 

 heat quite sufficient to roast a sirloin of beef if placed in 

 the position of the pudd^s hands, is beyond comparison 

 with that which would be demanded of a collier working 

 even at a depth giving a theoretical rock temperature of 

 212, and aided by the coal-cutting and other machinery 

 that sufficiently high prices would readily command. In 

 some of the operations of glass-making, the ordinary sum- 

 mer working temperature is considerably above 100, and 

 the radiant heat to which the workmen are subjected far 

 exceeds 212. This is the case during a "pot setting," 

 and in the ordinary work of flashing crown glass. 



As regards the mere endurance of a high temperature, 

 the well-known experiments of Blagden, Sir Joseph Banks, 

 and others have shown that the human body can endure 

 for short periods a temperature of 260 F., and upwards. 

 My own experience of furnace-work, and of Turkish baths, 



