Mr. Riley's Reply to the Rev. Mr. Graves' notice of Hoveden did not reach us in time for insertion this week.
I. A. N. (93rd Highlanders.) Several correspondents, as well as yourself, complain of the difficulty of obtaining amber varnish. There are several Eastern gums which much resemble amber, as also a substance known as "Highgate resin." Genuine amber, when rubbed together, emits a very fragrant odour similar to a fresh lemon, and does not abrade the surface. The fictitious amber, on the contrary, breaks or becomes rough, and has a resinous turpentine-like smell. Genuine amber is to be obtained generally of the tobacconists, who have often broken mouth-pieces by them: old necklaces, now out of use, are sold at a very moderate price by the jewellers. The amber of commerce, used in varnish-making, contains so much impurity that the waste of chloroform renders it very undesirable to use. The amber should be pounded in a mortar, and, to an ounce by measure of chloroform, add a drachm and a half of amber (only about one-fourth of it will be dissolved), and this requires two days' maceration. It should be filtered through fine blotting-paper. Being so very fluid, it runs most freely over the collodion, and, when well prepared and applied, renders the surface so hard, and so much like the glass, that it is difficult to know on which side of the glass the positive really is. The varnish is to be obtained properly made at from 2s. to 2s. 6d. per ounce; and although this appears dear, it is not so in use, so very small a portion being requisite to effectually cover a picture; and the effects exceed every other application with which we are acquainted,—to say nothing of its instantaneously becoming hard, in itself a most desirable requisite.
—— (Islington). Your note has been mislaid, but in all probability the spots in your collodion would be removed by dipping into the bottle a small piece of iodide of potassium. Collodion made exactly as described by Dr. Diamond in "N. & Q.," entirely answers our expectations, and we prefer it, for our own use, to any we have ever been able to procure.
J. M. S. (Manchester) shall receive a private communication upon his Photographic troubles. We must, however, refer him to our advertising columns for pure chemicals. Ether ought not to exceed 5s. 6d. the pint of twenty ounces.
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