113 
Dr. Joule exhibited a camera, which was an improvement 
on the one described in the Photographic Notes, September, 
1 856. The body of the camera consists of a mahogany box 
holding a wide glass bottle, which is made use of to hold the 
silver solution. The plate is sensitised by turning the 
camera on its back, which causes the nitrate of silver to flow 
over it. 
Mr. Montefiore described some experiments which he 
had made for enlarging negatives by aid of the magic lantern, 
using magnesium, wire for the illuminating power. The 
wire had been found to bum very steadily in a jet of ordinary 
gas. 
Mr. A. Brothers, F.R.A.S., read a paper entitled “Was 
Daguerre a Discoverer?” 
Mr. Sidebotham read a paper “ On the proper focus of 
lens to be used in taking photographic landscapes, also on 
some modes of measuring the size of objects therein depicted.” 
The object of the paper was to shoAv that neither lenses of 
very long or very short focus give correct perspective, the 
former making distant objects appear too near, and the latter 
just the contrary. Lenses of less focus than 7 inches, and 
greater than 14, make this defect painfully visible. 
The latter portion of the paper advocated the placing a 
rod or mark of such a length, and in such a position in the 
picture, that it could be used as a scale of measurement for 
the principal objects. Also that a correct scale be made for 
each focus of lens, by placing poles of measurement at the 
distance of 100 yards apart, and marking each 10 yards 
distance from the camera, so that Avhen once the scale Avas 
formed, all photographs taken by that focus of lens (the 
