156 Proceedings of Learned Societies. 



to 60 times ; and aniseed 372 times the natural amount : hence the 

 perfume arising from a bed of flowers increases the temperature of 

 the air around them by rendering it more absorptive of radiant solar 

 heat. The vapour of water, when present, increases the absorption 

 of heat by the air in a very extraordinary degree ; during the month 

 of October last Dr. Tyndall found that the atmosphere was 60 times 

 more absorptive than dry air, owing to the continued moisture. Dr. 

 Tyndall infers that as the amount of vapour diminishes rapidly at a 

 distance from the earth's surface, the sun's rays are not sensibly 

 arrested until they reach our atmosphere, but that, on the other 

 hand, the heat of the earth is prevented from being radiated into the 

 free space and lost, by the existence of vapour in the air ; and owing 

 to the influence of this action, he thinks that even those planets 

 most distant from the sun may have a temperature sufficiently high 

 to render them inhabitable. 



CHEMICAL SOCIETY.— February 6. 



Formation of Siliceous Minerals. — Several interesting com- 

 munications were made to this Society. Professor Bloxam, of King's 

 College, read a paper on the presence of arsenic in sulphuric acid, 

 and the great difficulty of obtaining chemical substances absolutely 

 free from that element. Mr. Dugald Campbell, in the discussion 

 which followed, made an interesting statement relating to the almost 

 invariable presence of arsenic in hydrochloric acid, and traced its 

 orio-iu to the sea-salt used in the manufacture of that acid : arsenic, 

 as is well known, being, in common with silver, copper, etc., an in- 

 variable constituent of the waters of the ocean. In all the above 

 cases the arsenic exists in a proportion far too minute to be dis- 

 coverable except by the most delicate tests. Mr. A. H. Church then 

 gave the results of some experiments on the aqueous solution of 

 silica, which chemists are now able to prepare of considerable 

 strength by means of the dialytic process of Professor Graham. He 

 found that a solution containing three per cent, of dry silica, or flint, 

 was as transparent and nearly as mobile as water, when freshly mnde, 

 but that it soon became of the consistency of glycerine, and finally, 

 after six days, gelatinized completely. A very large quantity of the 

 pure aqueous solution of silica may be changed from the liquid into 

 the solid state in the course of ten minutes by the fifteen-thousandth 

 part of a grain, or less, of carbonate of lime ; the process of the 

 transformation into a firm jelly of several ounces of the limpid 

 solution by means of a few minute particles of the carbonate of an 

 alkaline earth being very remarkable. Mr. Church pointed out the 

 important geological effects which might have had their origin in an 

 aqueous solution of silica, referring more especially to the formation 

 of an interesting mineralized fossil known as " Beekite." This 

 substance, originally coral or shell, has been transformed into chale- 

 dony or flint, having lost nearly all its carbonate of lime. Mr. 

 Church had succeeded in effecting a similar transformation in recent 

 coral by means of the infiltration of an aqueous solution of silica. 



