136 Annals of the Philosophical Club 



tribute from them. The town Timbuctoo has a resident 

 population of above 13,000 persons, and a shifting one of 

 about 10,000. 



At the 95th meeting (June nth) General Sabine read a 

 letter from the Archduke Maximilian of Austria, thanking 

 English men of science for the interest they had taken in 

 the preparation of the exploring expedition of the Novara. 

 All the instruments, which had been prepared and verified 

 in England, had been safely received, and the vessel had 

 reached Gibraltar, which was to be its basal station for 

 magnetic observation on the voyage to the Cape of Good 

 Hope. 1 



Mr. Grove, at the 97th meeting (Nov. I9th) said that r 

 during the past autumn, he had discovered the skin of a 

 newly captured trout to have photographic properties. 

 When leaves, or other objects, were pressed upon the skin^ 

 on either side of the upper part, they left a very perfect 

 outline, which was negative in character, the darkest portions 

 being those more exposed to the light. No such impressions 

 appeared on the under surface. Professor Huxley thought 

 that the effect might be due to contraction of the chroma- 

 tophores (sacculae containing colour) upon the surface of the 

 fish. Dr. Carpenter and Dr. Sharpey thought the suggestion 

 worth following up, but said that chromatophores had not 

 yet been actually found in the trout's skin. 



Professor Tyndall described an ascent of Mont Blanc made 

 during last autumn, 2 when he and his companions had felt 

 extreme prostration during the last part, having to halt 

 after each fifteen steps. He called attention to the blue 

 tint seen in a hole made by thrusting an alpenstock into 

 the snow. 



At the 98th meeting (Dec. I7th) Mr. Horner gave further 

 particulars about the borings in the Nile Valley. Fragments 

 of coarse pottery had been found at a depth of 45 feet. 

 Taking as a basis for calculation the statue of Rameses II. 



1 The expedition returned in 1859 after about three years' voyage, and 

 the results were published 1862-77. 



2 An account of it is given in Glaciers of the Alps, part i. sect. n. 



