509 



Bowley-ragg. 7. Ancient porphyritic lava, containing numerous 

 crystals of hornblende, from Vesuvius. 8. A specimen of tufa, or 

 volcanic mud, also from Vesuvius. 



The author infers from his analysis that phosphoric acid is a very 

 usual component part of volcanic rocks, and is a principal source of 

 the remarkable fertility possessed by soils derived from their disin- 

 tegration. 



May 2, 1844. 



The MARQUIS OF NORTHAMPTON, President, in the Chair. 



1. "Ranges of the Barometer and Sympiesometer on board 

 H.M.S. ' Alfred,* in the River Plate, between the 1st of July and 

 the 31st of December, 1843." Communicated by Captain Beaufort, 

 'R.N., F.R.S. 



This paper is a register of the results of daily observations of the 

 heights of the barometer, sympiesometer and thermometer, the direc- 

 tion of the wind, and state of the weather during the above period. 



2. " Remarks on the amalgamation of Silver Ores in Mexico ; 

 with an account of some new combinations of Copper, Oxygen and 

 Chlorine." By John Christian Bowring, Esq. Communicated by 

 S. Hunter Christie, Esq., Sec. R.S. 



The process employed in Mexico for amalgamating ores con- 

 taining sulphurets of silver, and which consists in adding to them a 

 solution of bichloride of copper with chloride of sodium, is explained 

 by Sonneschmidt, Humboldt, and Boussingault, on the supposition 

 that a chloride of silver is formed at the same time that the sulphur 

 combines with the copper. The author calls in question the truth 

 of this theory, and proposes certain modifications of the process by 

 the employment of a combination of deutoxide of copper with the 

 bichloride, until an oxy-chloride is formed, and then adding finely 

 precipitated copper, by which a salt of a brick-red colour is ob- 

 tained, insoluble in water, and at a temperature of 200° Fahr. 

 speedily reducing sulphuret of silver to the metallic state. 



3. " Experimental evidence in support of the secretion of Carbon 

 by animals." By Robert Rigg, Esq., F.R.S. 



The author finds that the mean of the results of different experi- 

 mentalists as to the quantity of carbon excreted by respiration from 

 adults, during twenty-four hours, is 5963 grains ; whereas the 

 weight of the carbon contained in the whole of the food, both solid 

 and liquid, received into the body during the same period, as ascer- 

 tained by the analysis of each article of diet, made by the author, 

 falls very short of tha,t quantity ; varying in different cases from 

 3002 to 4800 grains. The same inference is drawn from experi- 

 ments made on a mouse, weighing 181 grains, confined in a wire 

 trap for twenty-eight days ; during which time it consumed food 

 containing 544*5 grains of carbon, and gave out, in the respired air, 



