: E.—GEOGRAPHY. , 139 
‘really affect the question of white versus black colonization, as there does 
‘not seem to be any reason to believe that black men could withstand a 
higher wet bulb temperature than white men. In answer to an inquiry 
‘on this question, Dr. J. §. Haldane replied that his impression on the 
‘contrary was that ‘white men can usually stand more heat than black 
men,’ and he reported the information given him that in places like the 
Red Sea the Clyde stokers stand the heat better than the Lascars, ‘ and, 
‘in fact, have constantly to carry the latter out and lay them on deck to 
‘cool.’ Dr. C. J. Martin also informs me that there seems no physiological 
‘reason why the conditions indicated by a high wet bulb temperature 
should be more adverse to the white man than to the coloured races. 
~ (€) Monotony in Temperature—Another temperature factor that has 
been appealed to is that depressing equability of temperature which occurs 
en some tropical coasts. Excessive monotony in the weather is no doubt 
depressing and temperature changes have a stimulating beneficial 
effect. Extremes of cold and heat are still more inconvenient and trying, 
and a moderate equability is often advertised as an attractive feature in a 
climate. The equability of the oceanic climate is recognized as most 
favourable for many conditions of health. The areas over which extreme 
uniformity of temperature prevails throughout the year are, however, so 
restricted that this factor does not affect the problem of tropical settlement 
-as a whole. With the exception of low tropical islands, places with 
monotonously equable climates are in positions whence a change may be 
secured by a visit to some neighbouring hill country. 
(d) Actinic Rays.—A fourth factor to which much importance has been 
attached in connection with the tropical climate is the effect of the 
chemical rays of the sun. Great importance was once attached to the 
: pernicious influence of the ultra-violet chemical rays of the sun on persons 
not protected by a dark skin. Residents in the tropics were therefore 
advised to line their clothes with orange-coloured fabrics to shield them- 
selves from the chemically active rays. These views reached their extreme 
in the writings of Surgeon-Major C. E. Woodruff in 1905 on the ‘ Effects 
of Tropical Light on White Men.’ Woodruff held that the actinic rays of 
the sun are so inimical to the white man that they inhibit his permanent 
settlement within 45° of the Equator. He therefore regarded the tip of 
Patagonia as the only area in the Southern Hemisphere fit for white 
occupation. The temporary stagnancy of the population of Australia 
after the droughts of 1900-1902 he regarded as evidence that the native- 
born white Australian and delicate New Zealander were wasting away 
_ through physical decay due to the enfeebling sunshine, just as the health 
of American and European children was being ruined by the ‘ daft’ 
_ practice, as he called it, of flooding schoolrooms and nurseries with streams 
_ of light. Woodrufi’s conclusions have naturally been disregarded. 
[ Any deleterious effects of the chemical rays of the sun may be avoided 
by the use of appropriate clothes, and physical considerations suggest 
that a black skin should afford less protection than a white skin. Any 
injury that may be wrought by powerful sunshine, according to Aron’s 
_ work in the Philippines, is due to the heat rays at the red end of the 
spectrum and not to the chemical rays. The modern lauded system of 
heliotherapy is based on the belief that strong sunshine is a powerful 
curative agency. 
