46 ~=British Association for the Advancement of Science. 
dissolving 1 grain of nitrate of silver in 500 of water, and apply- 
ing this solution like the browning liquid. 'The number of repe- 
titions of the nitrate of silver water would depend on the shade 
of brown required, but Mr. Ettrick found from 1 to 5 or 6 amply 
sufficient. The barrel is to be placed in the sunshine to obtain a 
dark color. The last process was to apply the scratch brush freely, 
though lightly, and then polish the whole by bees’ wax. Mr. Et- 
trick had, since the date of his own invention, discovered the pro- 
cess used by workmen generally, and long kept secret, but by the 
plan described a much finer brown is attainable than that gained | 
by the trade. — 
Fossil Fishes—Agassiz’s great work going on.—Mr. Dawson 
exhibited a collection of fossils from New South Wales.—Mr. 
Murchison communicated some information which he had lately 
received from M. Agassiz, who was bringing out some new livrai- 
sons of his great work on fossil fishes, and he mentioned that in 
order to enable that gentleman to carry on his work, a further 
grant of money would be recommended by the Geological Com- 
mittee. The remains of fish had been found to be the most valu- 
able of all indexes for determining the ages of rocks, as there was 
a plain separation of these animals in formations of different ages. 
Mr. Murchison showed drawings of some of these fossils, and re- 
marked that in the lias and the older beds the fishes were charac- 
terized by a tail quite different from that belonging to those found 
in the newer formations, and he exhibited on a board representa- 
tions of some of the peculiarities of those discovered in the Silu- 
rian rocks. He must record the names of Drs. Lloyd and Lewis 
as having given him material assistance in the collection of these 
remains. He had found remains like the shagreen or tubercula- 
ted skin of some recent fishes, also extraordinary teeth belonging 
to a species termed Stogodus Priscodontus, and fish called Sera- 
plum, by the quarrymen, froma their seeming to possess only head 
and wings, to which the name Pterigodus has been given; also 
many others which M. Agassiz would soon have described and 
published. 
Heat in Mines.—Mr. R. W. Fox stated, that at the Bristol 
Meeting of the Association he had been requested to make ex- 
periments on the Electricity of Mineral Veins. He had been un- 
able to. do much since that time—he had merely to mention, that 
he had made experiments at Middleton Teesdale, in the county of 
