60 NOTICES OF THE MEETINGS. ([A4pri/ 11, 1851. 
amount of change in the conducting power of the air for given 
changes of temperature, and then to apply that in the endeavour to 
ascertain whether the amount of change to be expected is (as well 
as the direction) accordant with that which really occurs. 
In the Library were exhibited :— 
Gilbert, de Magnete; Kircher, de Arte Magnetica ; Churchman’s 
Magnetic Atlas; and the Magnetical Observations at Greenwich, 
St. Helena, Toronto, and Bombay; and Col. Sabine’s ‘‘ Unusual 
Magnetic Disturbances’’ [from the Royal Institution Library]. 
Minerals from Texas, collected and presented by W. Bollaert, Esq. 
Portrait of Mr. Faraday by A. Blaikley, Esq. 
Candelabras presented to the Marquis of Tweeddale [by Messrs. 
Hunt and Roskell]. 
Model of Anchor invented by Commander Inglefield, R.N. M.R.I. 
Fairburn’s Machine for Making Cotton-Cards [by Mr. Fairburn, 
C. E.] 
“A Retriever ;”’ First Proof of an Engraving by H. T. Ryall, from a 
Drawing by Sir E. Landseer [by Mr. J. L. Grundy]. 
New Water-mark in Bank-note paper, and Specimen of Paper split 
in three [by Mr. Oldham}. 
Nine Flints with Fossil Sponges, &c. from Salisbury; a large piece 
of Native Copper, with Native Silver, Calcareous Spar &c. part 
of a piece weighing 30 tons from Lake Superior [by Mr. Tennant]. 
Talbotypes and Photographs [by Messrs. Henneman and Malone]. 
