Miscellaneous. 103 
from the sunshine. It was then carefully washed. All that part 
of the metallic silver on which the solution had been suffered to 
dry in the sun was pure steel-grey, whilst that which was removed 
still wet had a strong reddish bloom.” ‘The contrast remained 
permanently, and evidently depended upon some difference of 
molecular arrangement. ‘It-would be interesting to observe,” 
says Mr. Lea, in connection with this, “whether negatives are 
dried in the sun or not thereby somewhat different from the same 
or corresponding negatives dried in the shade; and, also, whether 
positive proofs on paper could not be affected for good or for evil 
by drying in the sun.”—J. W. W. in “ Science Gossip.” 
Varieties In Inx.—Gold ink is made by grinding upon a por- 
phyry slab, with a muller, gold leaves with white honey, till they 
become reduced to the finest possible division. ‘The paste is then 
collected upon the edge of a knife or spatula, put into a large 
glass, and diffused through water. The gold by gravity soon falls 
to the boitom, while the honey dissolves in the water, which must 
be decanted off. The sediment is to be repeatedly washed till 
entirely freed from the honey. The powder, when dry, is very 
brilliant, and when to be used as an ink, may be mixed up with a 
little gum water. After the writing becomes dry, it should be 
burnished with a wolf’s tooth.—Silver ink is prepared in the same’ 
manner.—Indelible Ink: A very good ink, capable of resisting 
chlorine, oxalic acid, and oblution with a-hair pencil or sponge, 
may be made by mixing some of the ink made by the preceding 
prescription, with a little genuine China ink. It writes well. 
Many other formulz have been given for indelible inks, but they 
are all inferior in simplicity and usefulness to the one now pre- 
scribed. Solution of nitrate of silver thickened with gum, and 
written with upon linen or cotton cloth, previously imbued with 
a solution of soda, and dried, is the ordinary permanent ink of 
the shops. Before the clothes are washed, the writing should be 
exposed to the sunbeam, or to bright daylight, which blackens 
and fixes the oxide of silver. It is easily discharged by chlorine 
and ammonia. A good permanent ink may be made by mixing a 
strong solution of chloride of platinum with a little potash sugar, 
and gum to thicken. The writing made therewith should be 
passed over with a hot smoothing iron, to fix it. Nitrate of 
silver, 1 to 2 dr.; water, # oz.; dissolve, add as much of the 
strongest ammonia water as will dissolve the precipitate formed 
on its first addition, then further add mucilage, 1 or 2 drachms, 
and a little sap green to colour. Writing executed with this ink 
turns black on being passed over a hot Italian iron. Asphaltum, 
I part; oil of turpentine, 4 parts; dissolve,. and colour with 
printers ink. Yery permanent.—“ Paper Trade Review.” 
A Law oF ComBustTion.—Numerous and careful experiments 
have developed the law that the heat generated by the burning of 
any substance is pretty nearly in proportion to the weight of 
oxygen with which the substance combines in burning. For 
