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.—Cuemisrry anp Mineracoey. 
Dr. Daubeny read an interesting report on the present state of 
our knowledge with respect to mineral waters. 
r. Mushet 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 
r. 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 @ 
pamphlet on the Berzelian nomenclature, which be addressed some 
years since to Prof. Silliman. 
Section C.—Gro.tocy anp Grocrapny. 
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 exenieed the speci- 
