AND ETHER WAVES. 93 



illustration hitherto adduced of the conservation of 

 molecular action. 



Thus, by new methods of search, we reach a result 

 which was long ago enunciated on other grounds. 

 Water is well known to be one of the most opaque of 

 liquids to the waves of obscure heat. But if the re- 

 lation of liquids to their vapours be that here shadowed 

 forth — if in both cases the molecule asserts itself to be 

 the dominant factor — then the dispersion of the water 

 of our seas and rivers as invisible aqueous vapour in our 

 atmosphere, does not annul the action of the molecules 

 on solar and terrestrial heat. But as aqueous vapour is 

 transparent — which, as before explained, means pervious 

 to the luminous rays — and as the emission from the sun 

 abounds in such rays while from the earth's emission 

 they are wholly absent, the vapour screen offers a far 

 greater hindrance to the outflow of heat from the earth 

 towards space than to the inflow from the sun towards 

 the earth. The elevation of our planet's temperature 

 is therefore a direct consequence of the existence of 

 aqueous vapour in our air. Were that garment re- 

 moved, terrestrial life would probably perish through 

 the consequent refrigeration. 



I have thus endeavoured to give some account of 

 recent incursions into that ultra-sensible world — the 

 world of the ' scientific imagination ' — mentioned at 

 the outset of this paper. Invited by my publishers, 

 with whom I have so long worked in harmony, to send 

 some contribution to the first number of their new 

 Magazine, I could not refuse them this proof of my 

 good-will. 



Note. — The researches glanced at in the foregoing brief article 

 have been published in externa in the ' Philosophical Transactions.* 

 I would invite to them and others, in their correct historical sequence, 

 the attention of my friend Professor Von Hofmann. 



