Mae. 12. 1853.] 



NOTES AND QUERIES. 



267 



one any further information, either privately, or 

 through " N. & Q." It seems to me that by this 

 contrivance you simplify the process as much as 

 is almost possible ; you keep separate the different 

 processes, and run little or no risk of mixing your 

 chemicals, a misfortune which would spoil several 

 hours' work, as well as entail a considerable loss of 

 materials. The box would be no expensive ar- 

 ticle ; any one possessing a little mechanical skill 

 could construct it for himself, and its use as a 

 packing-case for your apparatus would repay the 

 cost. 



I have for some time been using a developing 

 fluid, which appears to have some desirable quali- 

 fications ; for it is simple, inexpensive, and keeps 

 good, as far as I have tried it, for a very long period. 

 i have worked with it when it has been made ten 

 weeks; it slightly changes colour, but it throws 

 down no deposit, and does not ever stain the film ; 

 when first made, it is colourless as water. De. 

 Diamond has kindly undertaken to test its value, 

 and if he pronounces it worthy of being made 

 known, the readers of "N. & Q." shall shortly 

 have the benefit of it. J. L. Sisson. 



Edingthorpe Rectory, Norfolk. 



New Effect in Collodion Pictures. — In the 

 course of some experiments I have been follow- 

 ing in reference to a photograpic subject, a 

 method by which a new effect in pictures on glass 

 may be obtained has occurred to me. Such pro- 

 ductions, when treated as positives, are of course 

 white pictures upon a black ground ; and although 

 for beauty of detail they are superior to those 

 belonging to any other process, there is a certain 

 harshness and want of artistic effect : to remedy 

 this, I turned my attention towards obtaining a 

 dark picture upon a light ground, as is the case 

 when glass photographs are printed from ; in this 

 I have succeeded, and as the modification affords 

 a pleasing variation, it may be acceptable to the 

 tastes of some of your readers. The principle I 

 proceed upon is to copy, by means of the camera, 

 from a previously-taken picture in a negative 

 state. Suppose, for instance, our subject is an 

 out-door view : I take a collodion picture — which 

 would answer for a positive if backed with black : 

 this, viewed by transmitted light, is of course 

 negative, — an effect which may be produced by 

 placing a piece of white paper behind it from 

 this wMe-backed plate : I take another collodion 

 picture, which, being reversed in light and shade, 

 is negative by reflected light ; but viewed as a 

 transparency is positive, and of course retains 

 that character when backed with white paint, 

 paper, or other substance lighter in colour than 

 the parts formed by the reduced silver. Instead 

 of the first picture being formed by the glass, any 

 of the paper processes may be adopted which will 

 afford negative pictures. Copies of prints may be 



beautifully produced on this principle by obtain- 

 ing the first or negative by the ordinary process 

 of printing. As these pictures are to form a con- 

 trast with a white ground, they should be as 

 brown in tint as possible ; nitric acid, or other 

 whitening agents, being avoided in the developing 

 solutions for both negative and positive. By this 

 process the detail and contrasts can be kept far 

 better than by the operation of printing : for it is 

 exceedingly difficult to obtain a picture which will 

 convey to the prepared surface an amount of light 

 corresponding to the natural lights and shades, 

 and the trouble of making collodion copies is far 

 less than printing. There is certainly the draw- 

 back of having the copies upon glass : I think, 

 however, that some white flexible substance may 

 be found, upon which the collodion, albumen, &c., 

 may be spread ; but if they be intended for fram- 

 ing, of course they are better on glass. The 

 general effect is that of a sepia drawing. The 

 picture first taken and used as a negative, may be 

 preserved as a positive by removing the white 

 back, and treating it in the usual manner. 



Permit me to observe, that much confusion 

 arises from the manner in which the terms positive 

 and negative are often used ; a negative glass 

 picture is frequently spoken of as a definite, dis- 

 tinct thing ; this is not the case, for all photo- 

 graphic pictures upon glass are both negative and 

 positive, accordingly as they are seen upon a back 

 of lighter or darker shade than the reduced silver 

 — by transmitted or reflected light. A picture 

 intended to be printed from is no more a negative 

 than another, its positive character being merely 

 obscured by longer exposure in the camera. 

 When first removed from the developing solution, 

 glass pictures are negative, because they are seen 

 upon the iodide of silver, which is a light ground. 

 This is a thing of course well known to many of 

 your readers, but beginners are, I know, often 

 puzzled by it. Wm. Tudob Mablet. 



Manchester. 



Powdered Alum — How does it act ? — Sir W. 

 Newton has again kindly informed me of his 

 motive for using the powdered alum, which in 

 "N. & Q." (Vol. vii,, p. 141.) he asserts readily 

 removes the hyposulphite of soda. What is the 

 rationale of the chemical action upon the hypo- 

 sulphite of soda ? W. Adrian DELrEBiEE. 



40. Sloane Square. 



"^t^liti to j^tnor ^utxiti, 



Chatterton (Vol. vii., p. 189.).— J. M. G. informs 

 N. B. that he is possessed of the whole of the late 

 Mr. Hazlewood's collection of volumes, tracts, and 

 cuttings from periodicals, published during the 

 period when the Rowieian and Chattertonian con- 



