97 
Mr. SiDEBOTHAM exhibited a large sheet of photo- 
lithographs, executed by Mr. Dean, of Douglas, Isle of Man. 
They consisted of copies of wood engravings, copper-plate, 
pen drawings, writing, music, and letter-press, all copied by 
the camera and then transferred to stone, and printed in the 
ordinary manner with printing ink. Mr. Sidebotham said he 
considered this by far the best specimen yet exhibited, from 
the extreme sharpness of the lines, and thought as this was a 
branch of art likely to be much used, it was of great interest 
to see its present state of perfection. He also called attention 
to the great facility this plan offered to the forger of Bank 
notes, &c. : hitherto, although there was no difficulty hi getting 
a perfect facsimile of a note or cheque, the fact of its being 
printed on paper by silver or iron salts made its detection 
easy ; now that printing ink could be used a perfect facsimile 
in every respect could be made, so far as the printing is 
concerned. Mr. Sidebotham thought some steps should be 
taken in the matter, and suggested as (he most simple mode 
of defeating the photographer to use yellow paper and print 
in blue. So far as at present known, there would be no 
possibility of copying such a document by any process of 
photography. 
Mr. Sidebotham read a Paper li On the Planet Mars,” 
by James Nasmyth, Esq., and exhibited at the same time 
a large drawing of the planet, as seen by Mr. Nasmyth on 
the evenings of September 25th and October 11th, 1862, 
by the aid of his tine reflecting telescope of twenty inches 
diameter. Mr. Nasmyth called special attention to the patch 
of snow, as it was considered to be, at the south pole of the 
planet. This was unusually bright and round, like a white 
wafer on the pole of a globe ; it had also a cliff-like edge. 
This supposed patch of snow does not coincide with the true 
pole of the planet, but, like the arctic poles of the earth, or 
poles of minimum temperature, is slightly eccentric. 
