ACCLIMATIZATION. 673 



pro mille from 1837 to 1848, so that Boudin, Bertillon, and Knox 

 doubted \f the French could ever colonize there. At the present 

 time the birth-rate even exceeds that in France itself ; * and the 

 death-rate is but little above the normal, f In Tunis also the 

 birth-rate was 35*6 pro mille in 1890-'92, greatly exceeding the 

 ruling death-rate of 25'7 per thousand. J In America it is in the 

 uplands of Mexico, Peru, and Bolivia, or along the arid coast of 

 the Pacific, and not in the real tropical climate of Brazil, where 

 the Spaniards have succeeded most fully. They have also done 

 well in Cuba, to be sure, but the cases are entirely dissimilar. 

 And to reason, from the French success in Algeria, that the same 

 would ensue in the Congo basin, in Madagascar, or in Cochin China 

 is totally to misconceive the real limitations of a tropical climate.* 

 The relative difficulties to be encountered in these several cases 

 may be roughly indicated by the mortality of soldiers. In Cochin 

 China it is almost exactly double that in Tunis ; || and this is, 

 roughly speaking, a measure of the difference between a mere 

 torrid climate as distinguished from one which is very humid as 

 well as hot, for humidity means that malaria is superadded to all 

 the other difficulties inherent in climate alone. 



The heat in a tropical climate becomes important but indi- 

 rectly, because it is the cause of humidity and generally accom- 

 panies it. In the temperate regions humidity goes with cool 

 weather except in the dog days, while within the tropics heat 

 prevails just when radiation through perspiration is most retard- 

 ed by moisture in the atmosphere. This, in combination with the 

 enforced lack of exercise and its attendant excretion, forms the 

 double cause of physiologic disturbances. The blood is not prop- 

 erly purified and anaemia ensues, if the more immediate effects do 

 not manifest themselves in intestinal disorders. 



Everything which conduces to give a variety to the climate of 

 the tropics affords relief. The alternating sea and land breezes 

 of islands make them more amenable to European civilization. A 

 Especially when these islands are volcanic or mountainous is the 

 strength of these tempering elements increased. This, in fact, is 



* Levasseur, La Population fraiMjaise, iii, p. 43 ; and De Quatrefages, p. 229. 

 f Revue d'Anthropologie, third series, iv, p. 346. 



\ fitude statistique sur la Colonie de Tunisie, Tunis, 1894.; reviewed in L'Anthropologie, 

 r,p.731. 



* Vide Ravenstein in Proceedings of the Royal Geographical Society, January, 1891, pp. 

 80 el seq. Dr. Felkin has not always been clear on this (Scottish Geographical Magazine, ii, 

 p. 649). Refrigeration may do something as a palliative, but it deals with the lesser 

 factor. Vide address by President Galton before the Anthropological Institute, London, 

 1887. 



|| Revue d'Anthropologie, third series, iv, p. 346. 

 A Vide Jousset, p. 60. . 

 VOL XLvni. 48 



