364 Proceedings of the British Association, 



Prof. M'Cullagh made a communication respecting the laws of 

 double refraction in crystals of quartz. 



Mr. R. Addams then made a communication on the interference 

 of sound, and illustrated his subject by several experiments. 



Section B. — Chemistry and Mineralogy. 



Dr. Daubeny read an interesting report on the present state of 

 our knowledge with respect to mineral waters. 



Mr. Musbet exhibited some specimens of metallic iron, prepared 

 by exposing the iron ore to long continued heat, with a small quan- 

 tity of fuel, and thus reducing it to the metallic state without fusion. 



Mr. Johnston described paracyanogen and its compounds. 



Mr. West next read a short paper, the object of which was to sug- 

 gest a new mode of determining the presence, and estimating the 

 amount, of those materials which constitute but small fractional por- 

 tions of the atmosphere. His proposition was, that instead of ope- 

 rating upon a limited volume of air, as is usually done, a very large 

 quantity of it should be made by mechanical means to pass through 

 appropriate fluids — such as barytic water for carbonic acid, and ni- 

 trate of silver when the object was to determine the presence of mu- 

 riatic acid. — Dr. Dalton stated that he had for many years turned 

 his attention to the amount of carbonic acid in the atmosphere, and 

 that he had satisfied himself that its average quantity was one part in 

 1100. He altogether rejected the results of Saussure, and con- 

 tended that the quantity of this gas in the atmosphere was constantly 

 the same in town and country ; and that even in a crowded theatre 

 it seldom rises to one per cent. — Dr. Thomson gave it as his opin- 

 ion, that a fall of rain diminished the amount of carbonic acid in the 

 air, and expressed surprise that Dr. Dalton should maintain an op- 

 posite tenet. 



The business of the day was concluded by Dr. Hare reading a 

 pamphlet on the Berzelian nomenclature, which he addressed some 

 years since to Prof. Silliraan. 



Section C. — Geology and Geography. 



Mr. Stutchbury read a paper by himself and Dr. Riley, on some 

 newly discovered saurian remains, from the magnesian conglomerate 

 of Durdham Down. This communication chiefly related to the 

 specimens exhibited to the meeting, and contained a number of mi- 

 nute anatomical details, which testified in a high degree the industry 

 of Dr. Riley and Mr. Stutchbury, who had examined the speci- 



