138 SECTIONAL ADDRESSES. 
During some experiments by Sir Charles Blagden in 1774, Sir Joseph 
Banks remained in a room for seven minutes at a temperature of 211°; 
and Blagden subsequently stayed at the temperature of 260°, while eggs 
were roasted hard and beefsteaks cooked in a few minutes. White men 
work in furnaces and bakeries at 600° F., and if they can survive such 
temperatures even for short spells, they should be able to withstand the 
hottest climate on earth. 
That heat is not the dangerous factor in the tropics is obvious from the 
well-known fact that the hottest areas are often the healthiest. Agra is 
hotter and healthier than Bombay, and the summer heat of Colorado is 
fiercer than that in the less healthy Mississippi Valley. 
(b) Moist Heat—As dry heat affords no explanation of the high 
mortality of some tropical localities, appeal was made to moist heat, and 
to the combination of heat and moisture marked by a high wet bulb 
temperature. At any temperature above blood heat the body is cooled 
only by the evaporation of perspiration, which does not take place in air 
saturated with moisture. Hence in the Townsville experiments (‘Proc. 
R. Soe.,’ B.xci, 1920, p. 121), a man placed in a room in which the wet 
bulb temperature rose from 98° to 102°, fainted in forty minutes. In a 
hot locality a dose of atropin, which suppresses perspiration, may be 
quickly fatal. 
A wet bulb temperature higher than blood heat would be fatal to men, 
white or black; but no earthly climate has such temperatures. It was at 
first suggested that the limit of human activity was the wet bulb tem- 
perature of 73°. I have previously quoted ? well authenticated records 
of miners working for four-hour spells for months at the wet bulb 
temperature of 80° to 90° in Hongkong, the Straits Settlements, Beaufort 
in Borneo, and Ocean Island in the Pacific. At all these places people, 
both white and coloured, survive these conditions. Hence the limit has 
been gradually raised and it is recognized that men can withstand wet 
bulb temperatures of 85°, though the power of work under such conditions 
is necessarily greatly reduced. The highest wet bulb temperature 
mentioned in Dr. Griffith Taylor’s record at Port Darwin is 81°. The wet 
bulb data for North Australia are scanty; but there seems no reason to 
expect that any considerable areas have a more uncomfortable climate 
than Calcutta, to which Dr. Taylor compares the worst localities of 
tropical Australia. Calcutta is one of the healthiest cities in India, and 
has a large and vigorous European population, many of whom spend there 
the whole year. 
Moist heat is trying and must be considered in judging climates from 
the standard of comfort and personal efficiency. The investigation of 
wet bulb temperatures—the significance of which was shown by Dr. J. 8. 
Haldane, has been developed in reference to the textile industries by Dr. 
Leonard Hill and Dr. Boycott, to mining by Sir John Cadman, and to the 
conditions of tropical Australia by the work of Professor Osborne and has 
been illustrated by the ingenious climographs of Dr. G. Taylor—has 
yielded results of high practical value. But the wet bulb isotherm does 
not delimit the areas where the white man may live and work, and does not 
2 «The Wet Bulb Thermometer and Tropical Colonization.’ Journ. Scott. Meteor. 
Soc., ser. 3, vol. xvi, 1912, pp. 3-9. 
