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, I 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 asketch 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.—MarnHematicaL anp Puysicat 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 Rey. 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 
47 
Vou. XXXI.—No. 2 
