348 On the Colour of the Atmosphere and Deep Water 



as an historical monument, or to gratify the imagination of those 

 who are fond of referring to antiquity. 



osl address these reflections to foresters, naturalists, painters of 

 rural scenery, the local authorities of every nation. I request 

 them to measure the old trees with which they may be sur- 

 rounded, by the plans which I have proposed. All those who 

 have any means of publishing their results will act wisely in 

 printing them immediately, the only kind of register which at 

 present is destined to endure indefinitely. As to those who have 

 no facility in publishing, I offer to receive their observations, 

 and to register them in their names, either in this collection, or 

 in a particular work on the age of trees, materials for which I 

 have already collected. Those travellers who may not h^ix^' 

 ficiently acquainted with botany, so as to designate the tree by 

 the correct name, will do well to join to their measurements a 

 dried specimen of a branch in flower, which will serve as a label. 

 Those people who could send some specimens of the wood along 

 with them, which might aid in ascertaining the rate of their 

 growth, would afford means which might be of use in verifying 

 and comparing them. — Bib. Un.'MaS. 1831. 



ON THE COLOUR OF THE ATMOSPHERE AND DEEP WATER, BH, 



the Count Xavier de Mmstbe, 





The blue colour of the heavens is usually explained on the 

 supposition that the light of the sun, when reflected from the 

 surface of the. earth, is not entirely transmitted by the atmo- 

 sphere and lost in space, but that the molecules of the air reflect 

 and disperse the blue ray ; but no reason is assigned for this ray 

 being reflected in preference to the indigo or violet rays, whicH^^ 

 are more refrangible, and appear to be more easily reflected. '^:^ 



The same blue reflection is observed in the deep waters of the ' 

 sea ; and in those of lakes and rivers when in a limpid state. 



But these fluids are not the only substances which present 

 this singular phenomenon ; it is also found in bodies of a differei(i^^* 

 nature, and which appear to have no analogy to each other^.jf 

 OpaHne substances have generally a blue reflection *, and the < 



• The reflected colours which confer so tntich value on precious opal, have 



