J^8x? THOUGHTS ON THE 



for it goes entirely against it. " Les papillons diurnes de aos 

 iTiontagnes ont ordinairement le fond des ailes blanc ou d'un 

 brun plus ou moins fonce." It really is most astonishing that 

 this admirable entomologist should have so entirely forgotten 

 himself; he must, had he given it a moment's consideration, 

 have remembered that the intensity of light is much greater on 

 elevated ground, and that, owing to this very cause, the vine is 

 cultivated upon these mountains at an elevation which corre- 

 sponds, in mean temperature, to that of the plains four degrees 

 farther north than the extreme point at which, in the plains, it 

 prospers by the effect of the mean temperature alone. " If 

 the spaces, through which light passes in a uniformly dense 

 diaphanous medium, increase in arithmetical progression, the 

 quantity will decrease in geometrical progression." Hence we 

 can readily conceive how much more intense the light must be 

 on high mountains than in vallies, to reach which it has to pass 

 through some thousand feet of air, not uniformly, but increas- 

 ingly, dense, and, moreover, often humid. I should attribute 

 the changes to which he alludes more to the influence of tem- 

 perature than to that of light, yet we cannot doubt that this 

 last has some influence, for the diurnal Lepidoptera gain much 

 more in brilliancy than do the nocturnal. 



It is much to be regretted that naturalists, who visit foreign 

 climes, which afford most excellent opportunities for physiolo- 

 gical inquiries of this kind, mostly neglect them altogether, 

 contenting themselves with merely collecting new species, to be 

 described under barbarous half- Greek half-Latin names, by 

 some fireside naturalist. Oh for another Humboldt ! one who 

 would do for entomology what he has done for botany. But, 

 alas ! such men are rare, and seem only given us 



Ut in hoc infelici campo 

 Ubi luctus regnat, et pavor, 

 Mortalibus prorsus non absit solatium, 

 Hiijus eniin scripta evolvas 

 Mentemque tantaruni rerurn capacem 

 Corpori caduco superstitem credas. 



And now, to show my admiration of this great man, I am 

 going again to extract a passage from his " Tableaux de la 

 Nature." " The prodigious elevation, in tlie tropical regions, 

 not of isolated mountains alone, but also of entire countries, and 



