British Association for the Advancement of iScience. 297 



force over the earth's surface. The American observations were 

 made with needles inclosed in a vacuum apparatus, which Prof. 

 B. had devised, with the view of avoiding some of the anomalies 

 occasionally experienced by other observers. They were made 

 with extreme care, and were remarkable for minute attention to 

 all those circumstances which conduce to the accuracy of the 

 results. 



The secretary read Mr. Snow Harris's Report of Meteorolo- 

 gical Observatio7is tnade at Plymouth. Mr. E. Hodgkinson 

 gave several observations made the last year on temperature in 

 deep TTiines in Cheshire and Lancashire, a full report of which 

 he hoped to offer at the next meeting. Mr. Russell described an 

 apparatus for showing the con?iexion of magnetism loith the ^uind, 

 invented by Mr. Watt. 



Section B. Chemistry and Mineralogy. 



Dr. Thomas Thomson on Native Diarseniate of Lead. Du- 

 ring the meeting of the Association at Liverpool, a collection of 

 minerals from Alston Moor was exposed for sale. Among them ' 

 was one labelled, '' Vanadiate of lead from Caldbeck Fell." It was 

 in botryoidal concretions on quartz. Several of these nodules, 

 had, under the microscope, the aspect of cylinders. Color, honey- 

 yellow, like that of arseniate of lead, but lighter and much less 

 translucent. Lustre, resinous, and more brilliant than that of 

 vanadiate of lead. Does not scratch calcareous spar, but scratches 

 gypsum with great ease. Gravity, 7.272; that of vanadiate of 

 lead is only 6.663. Before the blowpipe on platinum foil, it melts 

 into a transparent globale, which on cooling, assumes nearly its 

 original appearance. On charcoal, it gives out abundant arsenical 

 fumes, and leaves globules of metallic lead. Two analyses by 

 Mr. Stenhouse gave, 



Chlorine, - 2.46 



Lead, ------- 7.10 



Arsenic acid, - - - - - 18.20 



Protoxide of lead, - - - - - 70.14 



Peroxide of iron, - - - - - 1.20 



Volatile matter, - - - - - 1.00 



100.10 

 Mr. Scanlan communicated observations on the Constitution 

 of the Commercial Carbonate of Ammonia. The results of his 

 YoL. XXXV.— No. 2. 38 



