1875-1876.] ! 79 



aqueous vapour is quite invisible, and is lighter than either oxygen 

 or nitrogen ; hence a falling and a low barometer indicates rain. 

 The latent heat of aqueous vapour is very great, nearly 1,000 de- 

 grees Fahrenheit. This, which simply maintains it in the state of 

 gas, without raising its temperature, is given back again as sensible 

 heat when condensation ensues ; and thus the heat of a tropical 

 sun, bottled up, as it were, in vapour raised there from the surface 

 of the sea, warms the air of higher latitudes where it is condensed. 

 In this manner aqueous vapour becomes a great modifier of 

 climate. After describing the properties of liquid water, the 

 reader observed that owing to its high specific heat, the sea is a 

 vast storehouse for the heat radiated by the sun within the tropics ; 

 and pointed out how countries surrounded by the ocean in tem- 

 perate latitudes, contrast as to the equability of their climates, with 

 other places on the same parallel, in the heart of a continent. 

 The curious behaviour of fresh water near the freezing temperature, 

 and in the act of freezing, as well as the peculiar deportment of 

 salt water in like circumstances, was mentioned as a clear proof of 

 creative design, no matter how some learned physicists might 

 deride the idea. Dr. Carpenter has shown by a beautiful experi- 

 ment, which the lecturer described, that the circulation of the 

 waters of the ocean, from the equator to the poles and back again, 

 depends mainly upon the fact that salt water, unlike that which is 

 fresh, contracts all the way down to its freezing^ point. Having 

 adverted to the climatic effects of oceanic circulation, the reader 

 described the properties of ice, the effects of frost and glaciers, 

 snow, &c. He then pointed out the chemical constitution of water, 

 and its action as a solvent on many of the solid materials in the crust. 

 Its effect when charged with carbonic acid upon felspar and calcic 

 carbonate was specially referred to. Limestone districts contain 

 caverns and underground rivers, as well as beautiful grottos, adorned 

 within in the most fantastic manner, by stalactites and stalagmites. 

 The water was shown to have actually made the grottos and 

 caverns, and the under-ground water courses, by dissolving away 

 limestone ; and the stalactites and stalagmites, by the evaporation 

 [M.0J3A0. n 



