1864. | Photography. 353 
portion of 1 to 180, half-a-second only being necessary to produce a 
similar picture in the daytime. 
The electric light, hitherto without a rival, is likely to be equalled 
in brilliancy, and far surpassed in convenience and cheapness, by the 
magnesium light. In our chronicles of the progress of optical science, 
we have given an account of this truly wonderful light, and we have to 
add here some notes respecting its photographic value. At a late 
meeting of the Literary and Philosophical Society of Manchester,* 
Professor Roscoe exhibited some prints of a portrait which Mr. 
Brothers and he had taken at 5 o’clock p.m., on the 22nd of February, 
by burning 15 grains of magnesium in the form of fine wire at a 
distance of about 8 feet from the sitter. The negative thus produced 
was stated by Mr. Brothers to be fully equal to any obtained by sun- 
light in the most favourable state of the atmosphere, and the distri- 
bution of light and shade was most agreeable, harshness of the shadows 
being completely avoided by slightly moving the wire whilst it was 
burning. The magnesium was worth about sixpence. Photographers 
are now eagerly asking for supphes of this metal, and if the wire can 
be got for anything like a reasonable price, there is no doubt that in 
this climate, at all events, this application of it is likely to inaugurate 
a new era in the photographic art. 
A very ingenious application of Professor Graham’s discoveries in 
the diffusion of liquids has been just made by Mr. Spiller. In washing 
photographie prints it has been noticed that the first portions of 
hyposulphite of soda are easily extracted, whilst the last portions are 
only removed from the paper with great difficulty. This is explained 
by the great diffusive power into plain water of a strong solution of 
hyposulphite of soda over a weak one. After the first portions of 
hyposulphite have been removed from the print, Mr. Spillert proposes 
to transfer them into a cold saline liquor made by dissolving a pound 
of salt in half-a-gallon of water; they are left there for fifteen or 
twenty minutes, when it is found that the salt brine has thoroughly 
penetrated the pores of the paper, and expelled the greater part of the 
remaining hyposulphite. The liquid is then poured away, and the 
prints are washed in common water. The principle of diffusion now 
comes into play again, and the salt brine rapidly soaks out of the 
paper, bringing with it the last traces of hyposulphite; by finally 
washing in the ordinary manner, an unusual degree of purity is 
attained, the presence of hyposulphite in the finished proof being 
rendered impossible. This is one of the most beautiful applications 
of a recondite scientific principle which we have ever seen. 
‘The detection of hyposulphite of soda in the finished proof, or in 
the last washings, is a matter of some importance. Mr. E. J. Reynolds 
has communicated to the ‘ British Journal of Photography,’ a series of 
experiments on the various methods at present in use. The first con- 
sists in reducing the hyposulphite to the state of sulphide by boiling 
* «Proceedings of the Literary and Philosophical Society of Manchester,’ 
No. 13, p. 241. 
+ ‘The Photographic News,’ vol. viii. p. 113. 
