348 NOTES OF A NATURALIST. 



a place of increasing commercial importance. Our 

 stay was so short that no one attempted to go ashore, 

 although the weather was favourable. Several whiles 

 were seen both on the 27th and 28th, but I failed to 

 ascertain to what species they belonged. 



On the evening of the 28th we experienced a 

 decided rise of temperature ; three hours after sunset 

 the thermometer still stood at 81° Fahr., and, with 

 two remarkable intervals, it did not fall below 80° 

 during the following eight days. During that time 

 my attention was often directed to the physiological 

 effects of heat on the human economy, and both my 

 own experience and the conflicting testimony of 

 travellers lead me to conclude that there are many 

 facts not yet satisfactorily explained. 



On the enfeebling effect of moist tropical climates 

 there is a general agreement, both as to the fact and 

 the chief cause ; but, as I have remarked in a pre- 

 ceding page, the circumstance that this is little or 

 not at all experienced at sea is apparently anomalous* 

 With regard to the direct effect of the sun's rays 

 on the surface of the body, and especially in the 

 production of sun-stroke, the evidence of scientific 

 travellers is conflicting, and the explanations offered 

 . are by no means satisfactory. On the one hand, it is 

 asserted on good authority that in the equatorial zone 

 the direct effect of the sun is far greater than it is 

 in Europe at the same elevation above the horizon. 

 The rapid reddening and blistering of the skin where 

 exposed, and sun-stroke from exposure of the head, 

 are said to be the ordinary effects. Being extremely 

 sensitive to solar heat, I have always carefully pro- 



