Page:Notes and Queries - Series 2 - Volume 1.djvu/69

 s. NO 3., JAN. 19. '56.]

NOTES AND QUERIES.

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tion of a name only renders an investigation some- what difficult. He refers me, for instance, to " Constable's reply to Courayer on this particular point." In what work of Constable is this reply to be found ? I am acquainted with one work only of Constable, viz. his Remarks upon F. Le Courayer s Book in Defence of the English Or- dinations, by Clerophilus Alethes (attributed to Constable') ; but this cannot be the work referred to by T. L., as it is a reply to Courayer's Dis- sertation, whereas the reference to Coke's charge by Courayer is in the second vol. of his Defence of the Dissertation, which I am not aware that Constable ever answered. And, after all, who was Constable ? A writer who implicitly believed, and unhesitatingly adopted the monstrous fable of the Nag's Head Consecration! a story utterly re- jected by Lingard himself as a palpable forgery ! History of England, vol. vi. p. 668., edit. 1849.

E. C. HARINGTON. The Close, Exeter.

PHOTOGRAPHIC CORRESPONDENCE.

AIM Desprats on Dry Collodion. The Abbe Desprats has addressed a communication to La Lumiere on the sub- ject of photography on glass with dry collodion. He considers that all the dry photographic processes (that is, albumen on glass, waxed paper, &c.) are founded on the same principles ; and that we have only minutely to inves- tigate those principles, and carefully to follow them out, to obtain the same results with dry collodion as with albumen or any other substance. The following process is the result of his experiments on that subject, and he considers that it can scarcely fail of success :

" The collodionized glass plate is sensitized for sixty or eighty minutes, as usual, in a sufficiently weak bath of nitrate of silver; four per cent, is quite strong enough. After taking it out of the sensitizing bath, the glass plate is carefully washed with distilled water. To do this, it is placed at the bottom of a shallow flat dish, the collodion side upwards; then gently covered with a centimetre, or more, of distilled water, and the saucer moved about gently for a minute or less. The plate is then taken out, and a stream of fresh distilled water poured on both sides, and then placed upright to drain on blotting-paper, and left to dry in complete darkness. When it is once dry, it can be acted upon by the light.

" The duration of the exposure varies according to the sensibility of the collodion. We have not remarked, in working the next day with the dry plate, that the sensi- bility had been perceptibly diminished, and less so than the wet plate would be.

" The image having been impressed on the glass plate, it is necessary to make it appear. This part of the pro- cess, which until now has been the cause of many failures, is by a very simple precaution the easiest thing In the world.

" Take the dish which was used for the first bath of distilled water, and, having emptied and washed it with care, pour into it two centimetres of fresh distilled water. Set the glass upright, near one of the edges, and lower it gently by means of a hook, the collodion upwards; move the plate up and down in draining it, and raising it by turns so as quite to assure the contact of the collodion and the liquid. Do this for a minute or more, until the

surface of collodion has become completely transparent. If by means of the feeble light passing through yellow glass, any bubbles of air are seen adhering to the surface of the collodion, the glass should be raised and the bub- bles got rid of by blowing the surface. The glass plate, having well imbibed the water, it should be let to drain gently by a corner, and submitted a second time to the first sensitizing bath. It should be left there longer than the first time, and the plate often moved up and down in the bath by means of a hook of silver or platinum, which should support it, and should be kept there all the time ; but in such a manner, as that the hooked part shall not touch the collodion ; scratches, however, are less to be apprehended than in the wet process. After sixty or eighty seconds of immersion, the plate is taken out and let to drain slightly ; it is put on a levelling stand, and covered immediately with pyrogallic acid, acidulated with crystallizable acetic acid in the ordinary proportions. The image will not be long in appearing ; at the end of five minutes perhaps the details will be nearly complete. At this moment pour the solution of pyrogallic acid into a small bottle, Avhere you have dropped several drops of a weak neutral solution of nitrate of silver of three per cent., and .cover the plate again with this liquid; the blacks become directly very strong, and the action of the bath must be stopped when the desired effect has been arrived at. The only thing now to be done, is to wash the plate with common water, and fix it by means of a saturated solution of hyposulphite of soda; and then wash it and dry it as usual."

These photographs, the Abbe" Desprats says, are re- markable for their beauty and regularity ; and there is much less danger of stains, &c., than with the wet pro- cess. He much prefers collodion to albumen ; and says, in fact, that the dry collodion process possesses all the advantages of other photographic processes, without any of their inconveniences.

He considers this process to be very applicable to printing on glass for. the stereoscope. On the collodion the lights are very clear, and the darks decided ; but great delicacy is necessary, owing to the degree of sensibility of the collodion, which ordinarily is too great. The sensitive- ness of the dry collodion is quite sufficient; for, in print- ing, sometimes even the fraction of a second is too much to expose it in full daylight ; and he has found it possible to print a positive from a negative on albumenized glass, by passing it for three minutes before the red flame of a candle. In printing, he considers it to be an advantage to have a collodion not very sensitive.

With collodion two years old, and that had turned red, he has obtained very good positives on glass by an ex- posure of scarcely a second to a moderately bright dif- fused light.

Photographic Society's Exhibition. We had purposed giving a detailed account of the beautiful series of Pho- tographic Pictures now exhibiting by this society ; but really the progress recently made by the art is so great the general excellence of the pictures exhibited so un- questionable that we must content ourselves with urging all who love truth and beauty to go and judge for themselves, reminding them (which it may be con- venient for many to know) that the Exhibition is open in the evening from seven till ten. One remark we must make, namely, that great as is its progress as an art ge- nerally, photography has made special progress in that division for which, as we have so long insisted on in this journal, it is particularly adapted namely, that of giving faithful representations of objects of antiquarian interest. Let the visitor examine Mr. Fenton's Cuneiform Inscrip- tions (of the size of the originals), and his other anti-