Proceedings of the British Association. 369 



tinental prices differed greatly from those in England, and, conse- 

 quently, that the amounts were comparative, and not absolute value. 

 The value of the mineral products of Europe, including Asiatic 

 Russia, were, — gold and silver, 1,943,000 ; other metals, 28,515,000; 

 salts, 7,640,000; combustibles, 18,050,000; making in round num- 

 bers a total of about fifty six millions, exclusive of manganese. Now 

 to this amount Great Britain contributed considerably more than 

 one half, viz. twenty nine millions, in the following proportions: — 

 silver, 28,500; copper, 1,369,000; lead, 769,000; iron, 11,292,000; 

 tin, 536,000; salts, 756,250 ; vitriol, 33,000; alum. 33,000; coal, 

 13,900,000. He then gave a sketch of the history of mining in 

 Great Britain, dwelling strongly on its vast increase since the intro- 

 duction of the steam engine. 



Evening Meeting at the Theatre. — The Secretaries having read 

 abridged reports of the proceedings of the Sections, a very interest- 

 ing letter was read from Sir John Herschel to Sir William Hamilton. 



Thursday, August 25. 



Section A. — Mathematical, and Physical, Science. 



Mr. Peacock read a Communication from Mr. Talbot " On the 

 Integral Calculus." 



Dr. Apjohn made a communication " On the use of the Wet- 

 bulb Thermometer, in determining the specific heat of air." 



Prof Sir. W. R. Hamilton then made a communication " On the 

 Calculus of Principal Relations." 



The Rev. Mr. Scoresby gave an account of two very delicate 

 Magnetic Instruments. 



Prof Forbes read a paper " On Terrestrial Magnetic Intensity at 

 great elevations from the earth." The author began by giving a 

 rapid review of Saussure's observations connected with this subject. 

 It was well known (he said) to men conversant with these researches, 

 that this enterprising philosopher and naturalist ascended Mont 

 Blanc, nearly at the summit of which he resided for many days, 

 making and recording numerous meteorological experiments, at an 

 elevation of about eleven thousand feet above the level of the sea ; 

 but when his observations upon the magnetic needle were properly 

 corrected, for the depression of temperature well known to exist at 

 these great elevations, the result of them was, that at this great ele- 

 vation there was no alteration of magnetic intensity which could be 



Vol. XXXI.— No. 2. 47 



