Temperature in Connection with Elevation, 443 



quiries. Two extracts from other parts of the count*s memoir 

 are here appended, as belonging to the subject before us, and 

 which it would be wrong to omit : — " Although the blue 

 colour of water is often marked by numerous causes, it is 

 sometimes exhibited in all its intensity : a fine example of it 

 is witnessed in looking at the Rhone from the bridge at Ge- 

 neva. The river seems to flow from an ultramarine source. 

 The spectator is in the most favourable situation for observing 

 the internal reflection, disengaged, as much as possible under 

 an open sky, from the reflection at the surface." (Griscom's 

 translation, Amer.Journ., xxvi. 68.) 



" The bluish green colour of crevices in the glaciers is 

 occasioned in the same manner as that of water near shore : 

 if the mass of ice were as great and homogeneous as that of 

 the sea, the interior of the crevices would be blue; but the 

 ice contains air-bubbles, particles of snow, and fissures, which 

 reflect the transmitted light, throwing it from one face to 

 another of the crevice, until it finds an escape. These opaque 

 substances in the glacier produce the same effect as a white 

 surface in the depths of the sea." {Ibid., p. 70.) That De 

 Maistre is correct may be shown by this, that our homeward- 

 bound ships can, when out of sight of land, distinguish their 

 approach to the Channel by observing the colour of the sea 

 change from blue to green. Captain Basil Hall (somewhere, 

 in one of his amusing works) speaks of the " reign of blue 

 water," to designate the deep open sea. Every one who has 

 happened to have been in a violent storm in the ocean, has 

 seen huge green waves approaching his vessel ; the water 

 composing which, in time of calm, would be blue. Seen 

 horizontally, the wave, by transmitted light, becomes gree?i. 



To sum up all, De Maistre concludes his remarks by 

 observing that the effects alluded to above appear to him "to 

 depend wholly on the peculiar property which the blue ray 

 possesses of being reflected, in preference to other rays more 

 or less refrangible, by the simple mechanical resistance of the 

 molecules of bodies which reflect light." (p. 75.) 



Stanley Green, Aug, 8. 1834. W. B. Clarke. 



Art. X. Data toxvards determining the Decrease of Temperature 

 in Connection with Elevation above the Sea Level, in Britain, 

 By H. C. Watson, Esq. F.L.S. 



We have very few data for determining the decrease of 

 temperature, either of the earth or atmosphere, in connection 

 with increase of elevation above the sea level : an enquiry 



