Another process of Herschel's is, to mix solution of nitrate silver of sp. gr. 1.200, with ferro-tartaric acid solution sp. gr. 1.023, till a precipitate falls which is re dissolved by heat, leaving a black sedi ment and a pale yellow liquor. This li quor undergoes no further alteration. This is spread on paper and exposed wet to sunshine for a few seconds, when it may be withdrawn. The image gradual ly comes out afterwards, and is very in tense. If dried before exposure in the camera, an invisible image is formed, which, on breathing upon, immediately appears, and, as if by magic, acquires great sharpness : instead of breathing upon it, it may be laid between the folds of wet paper.
Amphitype.-$o called because both po sitive and negative pictures are produced by it, is another process of Sir J. Hers chell's. The paper must be prepared with ferro-tartrate of mercury or lead, or ferro citrates of the same bases. The salts should be laid on in the state of cream : or, the paper may be saturated with ni trates of the oxides and then dipped in ammonio-citrate or tartrate of iron. Ne gative pictures are obtained by long ex posure, which are not permanent. When faded, it may be restored by dipping it in a solution of pernitrate of mercury till the original picture disappears, (this also requires a long time,) it is then well washed with water and dried, rubbed over with a hot iron between clean papers when a black positive picture at once ap pears. If the paper had been previously washed with uric acid the pictures pro duced are much better.
The juices of flowers have been found to be very sensibly effected by light and . to produce images by long exposure in the camera : this process is called antho type.
The following are correct directions for preparing Talbotype paper : Iodizing.-100 grains nitrate of silver dissolved in 8 oz. distilled water ; wash the paper evenly with a brush or clean cotton ; spread the paper on sheets of blotting paper, till quite dry. Then im merse it in a bath of iodide of potassium 1 oz. and a pint of water, leave it a very few seconds, not more than twenty ; then immerse it in distilled water for some minutes, and afterwards pin up by a cor ner and dry ; lastly, pin it up in the sun for at least an hour.
Preparing for Camera.—Wash with 1 part nitrate silver (proportion 50 grains to an ounce water): 6 parts of saturated solution of gale acid, 2 parts acetic acid ; take off superfluous moisture with clean white blotting pa pier.
To bring out Pieture.-1 part nitrate silver (50 grains to an ounce,) 3 parts sa turated solution gallic acid ; when finish ed wash in three clean waters ; and to fix temporarily, wash with bromide of potas sium ; proportion of solution 10 grains to 1 oz. distilled water ; after some minutes wash and dry.
For final Fixing.—Immerse in hot bath of 1 part of a saturated solution of hy posulphite of soda, to 10 parts water ia couple of minutes will bring out the io dine ; lastly, wash with three different hot waters, two or three minutes in each.
Copying Paper.-18 grains salt, dissol v ed in 1 pint distilled water ; soak the pa per in a bath of this and dry; then take 30 grains nitrate silver in 1 ounce distilled water ; add enough strong ammonia to make it turbid, then clear it by adding more ammonia ; with this solution wash your paper with a brush, when dry it is fit for the copying press.
To Fix.-10 grains hyposulphite soda, 1 ounce distilled water ; lay the copies in a bath of this after immersing them in 3 baths of warm water ; and after the by posulphite immerse them in three waters and then dry.
Chrysotype.—Paper is washed with a solution of ammonio citrate of iron and dried ; the paper should then be of a yel low color, (not brown,) and it is fit to take an image, which, when produced, is faint and hardly perceptible ; on removal from the camera, it is washed over with a solution of chloride of gold when the picture is produced, which afterwards darkens. It is then well rinsed with wa ter and washed over with a weak solution of hydriodate of potass.
Energiatype.—Aprocess of Mr. Hunt.— i Good letter-paper washed over with a solution of anemic acid 5 grains, 5 grains common salt, and half a dram of mucilage in 1 oz. of water : when dry, paper is drawn over the surface of 60 grams of ni trate of silver in 1 oz. distilled water. The paper is dried in the dark and fitted for use. It is of a permanent co lor ; 2 or 3 minutes is sufficient to take a portrait. The picture is brought out by passing the paper over a strong solution of proto-sulphate of iron thickened by gum. The paper is then well washed with water, and may be further fastened by weak ammonia or hyposulphite of soda.
Messrs. Langenheini, of Philadelphia, have discovered the art of making photo graphic pietires on glass, such as por traits, landscape views, copies of daguer reotypes, which is exactly similar to that described by M. Regnault, in behalf of M. Evrard, of Lille, who is said to have dis covered it in 1847. The principle of the discovery is a matrix of albumen, render ed sensible to the action of light, by ace to-nitrate of silver, and spread in a thin layer on a plate of glass. The process is to take a certain number of the white of eggs, and remove all the non-transparent part, and then add a few drops of a sa turated solution of iodide of potassium, then beat the eggs into froth and allow it to settle. The plate of glass is well clean ed with alcohol, and the albumen is then spread over the glass in a thin layer with another piece of glass. The glass must have a perfect thin coat adhering to it, when it is hung up by one of the corners to drain off the excess. The glass is then placed fiat upon a level board, screened from dust and allowed to dry. When dry it is submitted to a good heat, but not so much that the albumen will peel off. After this the glass is dipped into a solution of aceto-nitrate of silver, face downwards, after which it is removed and immersed in a basin of clean water, being stirred in it, for a few seconds, then taken out, held up by a corner, and is completely sensitive, moist or dry, to re ceive photographic impressions. It is then placed in the camera obscura, after which it is dipped in a bath of gallic acid, to which is added a little of aceto-nitrate of silver. Care is taken not to let the glass remain too long in this. After be ing dipped in the gallic acid it is washed in water and then immersed in a solution of the bromide of potassium (20 parts tc 100 of water), after which it is carefully and well washed in water, and left tc dry in a horizontal position in a dark room,