Hockin's Short Sketch.—Mr. Hockin is so well known as a thoroughly practical chemist, that it may suffice to call attention to the fact of his having published a little brochure entitled How to obtain Positive and Negative Pictures on Collodionized Glass, and copy the latter upon Paper. A Short Sketch adapted for the Tyro in Photography. As the question of the alkalinity of the nitrate bath is one which has lately been discussed, we will give, as a specimen of Mr. Hockin's book, a quotation, showing his opinion upon that question:

"The sensitizing agent, nitrate of silver in crystals, not the ordinary fused in sticks, is nearly always confessedly adulterated; it is thus employed:

"The silver or nitrate bath.—Nitrate of silver five drachms, distilled water ten ounces; dissolve and add iodized collodion two drachms.

"Shake these well together, allow them to macerate twelve hours, and filter through paper. Before adding the nitric acid, test the liquid with a piece of blue litmus paper; if it remain blue after being immersed one minute, add one drop of dilute nitric acid[[3]], and test again for a minute; and so on, until a claret red is indicated on the paper. It is necessary to test the bath in a similar manner, frequently adding half a drop to a drop of dilute acid when required. This precaution will prevent the fogging due to alkalinity of the bath, so formidable an obstacle to young hands."

Footnote 3:[(return)]

"Dilute nitric acid.—Water fifty parts, nitric acid one part."

Photographic Society's Exhibition.—The Photographic Society opened their first Exhibition of

Photographs and Daguerreotypes at the Gallery of the Society of British Artists, in Suffolk Street, with a soirée on Tuesday evening last. Notwithstanding the inclemency of the weather, the rooms were crowded not only by members of the Society, but by many of the most distinguished literary and scientific men of the metropolis. The Queen and Prince Albert had, in the course of the morning, spent three hours in an examination of the collection; and the opinion they expressed, that the exhibition was one of great interest and promise, from the evidence it afforded of the extraordinary advance made by the art during the past year, and the encouragement it held out to the belief that far greater excellence might therefore still be looked for in it, was a very just one, and embodied that given afterwards by the most competent authorities. We have not room this week to enter into any details, but can confidently recommend our readers to pay an early visit to Suffolk Street.

Replies to Minor Queries.

"Firm was their faith," &c. (Vol. viii., p. 564.).—These lines are to be found in a poem called "Morwennæ Statio, hodie Morwenstow," published by Masters in 1846, with the title of Echoes from Old Cornwall, and written by the Vicar of Morwenstow. I agree with D. M. in the judgment he has announced as to their merits; but hitherto they have been but little appreciated by the public. A time will come however, when these and other compositions of the author will be better known and more duly valued by the English mind.

Saxa.