SCIENTIFIC SUMMARY. 
515 
delicate tests, and carrying out a series of very carefully conducted experi- 
ments, from which he believes that all possible sources of error were 
eliminated, concludes that the application of peroxide of hydrogen to a print 
is in fact washing it in a very weak solution of sulphide of sodium, and 
thereby increasing the evil rather than decreasing it. Dr. Adrian, of King’s 
College, who has been conducting experiments on the action of peroxide of 
hydrogen and chlorine water on hyposulphites, has published the following 
laboratory notes : — 
Solution No. 1 . — One ounce of hyposulphite of soda to four of water. 
Solution No. 2.— Peroxide of hydrogen of the ten volume strength, very 
slightly acid. 
Solution No. 3. — Chlorine water, freshly prepared, and not quite saturated, 
also very slightly acid. 
“ Peroxide of hydrogen added in excess to the above strength of hyposul- 
phite solution did not, after the lapse of some hours, convert the whole of 
the hyposulphite into sulphite. Reactions with salts of silver and baryta 
proved this. No sulphite is formed as an intermediate stage of conversion. 
An appreciable trace of sulphur was liberated after some time. The smell of 
sulphurous acid evolved was also perceptible. Chlorine water added in excess 
to the same strength of hyposulphite solution behaved similarly, but more of 
the hyposulphite salt was decomposed ; so that the indications, namely, the 
precipitation of sulphur and liberation of sulphurous acid, which were only 
faint with peroxide of hydrogen, were much more marked with chlorine 
water.” Mr. Dawson, who conducted similar experiments, adds that “ in 
weaker solutions of hyposulphites, containing a fractional part of a grain of 
the latter in an ounce of water, the conversion into sulphate seems to be 
rapidly completed without any deposition of sulphur or liberation of 
sulphurous acid by both oxidizing agents.” The very small amount of 
soluble hyposulphites in even a large number of photographic prints renders 
their complete conversion into sulphates without decomposition by peroxide 
of hydrogen extremely probable, and Mr. Dawson hopes to demonstrate this 
in the course of yet further experiments. 
New Process of Photographing on Wood. — The Philadelphia Photographer 
gives the following as a reliable process : — Take a block of box- wood in the 
state in which it is prepared for the draughtsman, and saturate it with 
melted white wax for a few seconds only. Remove the wax with a scraper, 
and coat it with flake white. Then flow over it a solution of water three 
parts, albumen three parts ; to each ounce of which has been added three 
grains of salt. When dry, with a piece of paper you spread over it a solution 
of nitrate of silver, 15 grains to the ounce, acidified with two drops of glacial 
acetic acid to the ounce, and given the consistency of oil by the addition 
of a little gelatine. After again drying it is exposed to the fumes of 
ammonia for about fifteen minutes, and then printed on by the usual process. 
The print may be toned, but as this is not required we omit the process. It 
is fixed with hyposulphite of soda in the ordinary way. The Philadelphia 
Photographer says, “ By this simple and easy process quite a revolution is 
being made in wood-cutting, much to the improvement of the pictures.” If 
this is the case in America it is very unlike the case in England, for although 
