THE LIMITS OF OUR COAL SUPPLY. 227 



work of six or eight hours in a temperature of 130 F., provided I 

 were free from the encumbrances of clothing, and had access to 

 abundance of tepid water. This in a still atmosphere ; but with a 

 moving current of dry air capable of promoting vigorous evaporation 

 from the skin, I suspect that the temperature might be ten or fifteen 

 degrees higher. I enjoy ordinary walking exercise in a well-ventilated 

 Turkish bath at 150, and can endure it at 180. 



In order to obtain further information on this point, I have written 

 to Mr. Tyndall, the proprietor of the Turkish baths at Newingtoii 

 Butts. He is an architect, who has had considerable experience in 

 the employment of workmen and in the construction of Turkish 

 baths and other hot-air chambers. He sa3 T s : " Shampooers work in 

 my establishment from four to five hours at a time in a moist atmos- 

 phere at a temperature ranging from 105 to 110. I have myself 

 worked twenty hours out of twenty-four in one day in a temperature 

 over 110. Once for ono half-hour I shampooed in 185. At the 

 enamel works in Pimlico, belonging to Mr. Mackenzie, men work 

 daily in a heat of over 300. The moment a man working in a 110 

 heat begins to drink alcohol, his tongue gets parched, and he is 

 obliged to coninue drinking while at work, and the brain gets so 

 excited that he cannot do half the amount. I painted my skylights, 

 taking me about four hours, at a temperature of about 145 ; also the 

 hottest room skylights, which took me one hour, coming out at inter- 

 vals for " a cooler," at a temperature of 180. I may add in conclu- 

 sion, that a man can work well in a moist temperature of 110 if he 

 perspires freely." 



The following, by a writer whose testimony may be safely accept- 

 ed, is extracted from an account of ordinary passenger ships of the 

 Ked Sea, in the Illustrated News, of November 9th, 1872 : " The tern, 

 perature in the stoke-hole was 145. The floor of this warm region 

 is close to the ship's keel, so it is very far below. There are twelve 

 boilers, six on each side, each with a blazing furnace, which has to 

 be opened at regular intervals to put in new coals, or to be poked up 

 with long iron rods. This is the duty of the poor wretches who are 

 doomed to this work. It is hard to believe that human beings could 

 be got to labor under such conditions, yet such persons are to be 

 found. The work of stoking or feeding the fires is usually done by 

 Arabs, while the work of bringing the coal from the bunkers is done 

 by sidi-wallahs or negroes. At times some of the more intelligent of 

 these are promoted to the stoking. The negroes who do this kind of 

 work come from Zanzibar. They are generally short men, with 

 strong limbs, round bullet heads, and the very best of good nature in 

 their dispositions. Some of them will work half an hour in such P 

 place as the stoke-hole without a drop of perspiration on their dark 

 skins. Others, particularly the Arabs, when it is so hot as it often is 

 in the Red Sea, have to be carried up in a fainting condition, and rro 

 restored to animation by dashing buckets of water over them as they 

 lie on deck." 



It must be remembered that the theoretical temperature of 116 nt 

 4000 feet, the 133 at 5000 feet, or the 150 at 6000 feet, are the tem- 

 peratures of the undisturbed rock ; that this rock is a bad conductor of 

 heat, whose surface may be considerably cooled by radiation and 

 convection ; and therefore we are by no means to regard the rock 

 temperature as that of the air of the roads and workings of the deep 



