N.B.--Potash varying much in its alkaline property, some samples will remain colourless with addition of iodine; in which case the judgment must guide as to the quantity of iodine. It should not exceed the ounce of tincture: about two drachms may be added after using it for paper.
_Queries on Sir W. Newton's Process._--The process of SIR W. NEWTON is nearly similar to one I have successfully used for some years, and I can recommend it as effective and simple.
A difficulty I have lately found, has been with my iodized paper, which, when freshly used, is well enough; but if kept a month or two, will only allow of the paper being prepared to take views just before using. I should much like to know how this occurs.
If SIR W. NEWTON would answer the following Queries, he would add to the obligations that many others besides myself are under to him:
1. What paper does he use for positives, and what for negatives?
2. Is it not better to dissolve the silver and iodide of potassium in three ounces of water each instead of one (see "N. & Q.," Vol. vii., pp. 151. 277.)?
3. Is spring water fit for washing the iodized paper; if it contains either sulphate or bicarbonate of lime or muriate of soda?
4. How long ought the iodized paper to keep good?
5. How long should the negative paper (on a moderately warm day) keep after being made sensitive, before exposing to the action of light; and how soon after that should it be developed?
_Suggestion to Photographers._--The Rev. Charles Forster, in his _One Primeval Language_ (p. 96.), speaks of the desirableness of obtaining copies of two great inscriptions in the Djebel Mokatteb,--one in forty-one, the other in sixty-seven lines, supposed to have been written by the Israelites during their exode. In the words, however, of the Comte d'Antraigues, which he quotes in p. 84: "Il faudroit six mois d'un travail opiniâtre, pour dessiner la totalité de ces caractères." Is not this a temptation to some of your photographic friends, who may be turning their steps to the East during the ensuing season, to possess themselves of a treasure which by the application of their art they might acquire almost in as many minutes?
_Portrait of Pope_ (Vol. vii., p. 180.).--I cannot at this movement reply to MR. J. KNIGHT'S Query, but perhaps can correct an error in it. There was no _White_ of Derby; but Edward[9] _Wright_ of that city, was an artist of high repute. And I have in my possession a portrait of Pope done by him. On the back of this portrait is the following inscription: