Scientific Intelligence — Meteorology. 367 



On taking a mean of both sections for each series, giving each 

 section a value corresponding to its extent, it is found that the 

 number of feet of height corresponding to a fall of one degree Fahr- 

 enheit is- — 



On August 17 292-0 feet. 



August 26 290-7 „ 



October 21 291-4 „ 



November 10 312-0 „ 



The first three values being remarkably coincident, and the last 

 differing from them by about T Vth of the whole. 



The air collected in the ascents was analysed by Dr Miller ; he 

 states that "the specimens of air do not differ in any important 

 amount from that at the earth at the same time, but contain a trifle 

 less oxygen. All of them contained a trace of carbonic acid, but 

 the quantity was too small for accurate measurement upon the small 

 amount of air collected."- — (Proceedings of the Royal Society of 

 London.) 



11. Influence of Light upon the Colour of the Prawn. — A few 

 hours' captivity changes all the colours of the prawn ; all the fine 

 bands and stripes and spots become so pale as to be scarcely dis- 

 tinguishable from the general pellucid olive hue of the body. 



I cannot tell how this loss of colour is effected, but I have 

 reason to think that light, the great agent in producing colour, in 

 most cases is the cause. I took two specimens just dipped from 

 a deep pool, and equal in richness of their contrasted colours : one 

 of these I placed in a large glass vase of sea- water that stood on 

 my study table ; the other in a similar vase shut up in a dark 

 closet. In twenty-four hours the one that had been exposed to 

 the light had taken on the pale appearance just alluded to : the 

 one that had been in darkness had scarcely lost any of the richness 

 of its bands and stripes, though the general olive hue of the body 

 had become darker and of a brown tint. This individual, how- 

 ever, assumed the appearance of the former before it had been an 

 hour emancipated from its dark closet. Without attempting to 

 account for the phenomenon, I would just advert to the parallel 

 exhibited by the sea-weed. The brilliant colours displayed by 

 many of these exist, as is well known, in the greatest perfection, 

 when the plants grow at considerable depths, or in the caves and 

 holes of the rocks, where light can but dimly penetrate. 



Some of these will not grow at all in shallow water, or in a full 

 light, and those that can bear such circumstances are commonly 

 affected by them in a very marked degree — marked by the degene- 

 racy of their forms, and by the loss of their brilliancy of colour. 

 The prawn, as I have already hinted, delights in the obscurity of 

 deep holes and rocky pools ; it is here alone that his fine zebra-like 

 colours are developed. When taken in shallow pools, he is of the 



