46 



NOTES AND QUERIES. 



[No. 167. 



fineness to the paper, I employed for that purpose a 

 solution of iodide of potassium in alcohol of forty de- 

 grees saturated with collodion. 



" In continuing these studies I was induced to 

 apply this body upon glass, to obtain more fineness, 

 and I was soon in possession of an extremely rapid 

 proceeding, which I at last consigned to the pamphlet that 

 J published in 1850, and which was translated into En- 

 glish at the same time. 



" I had already at that time indicated the proto- 

 sulphate of iron for developing the image, the am- 

 monia and the fluorides as accelerating agents ; and I 

 was the first to announce having obtained by these 

 means portraits in five seconds in the shade. 



" The pyro-gallic acid is generally used now in place 

 of the sulphate of iron that I had indicated ; but this 

 is wrong, that last salt forming the image much more 

 rapidly and better, it having to be left less time in the 

 camera. 



" I believe, then, I have a right to claim for my 

 country and myself the invention of this would-be 

 English process, and of having been the first to indicate 

 the collodion, arid of giving the best method that has been 

 discovered up to the present time. 



" From the publication of my process, till my return 

 from the voyage that I had made for the minister, I 

 was little occupied in practising it, my labours on the 

 dry paper having taken all my time. This has been 

 used as a weapon against me, to make out that the first 

 trials before setting out had been quite fruitless, as they 

 had heard nothing more about it. 



" Nevertheless, I have made my discovery completely 

 public ; and if I had practised it but little, leaving it 

 to others to further develope, it has only been to oc- 

 cupy myself upon other works of which the public 

 has still profited. It is then much more ungenerous 

 to wish to take from me the merit of its invention." 



G. C, 



Ready Mode of iodizing Paper. — The readiest 

 way I have found of iodizing the beautiful paper of 

 Canson Freres, is the cyano-iodide of silver, made 

 as follows : Twenty grains of nitrate of silver may 

 be placed in half an ounce of distilled water, and 

 half an ounce of solution of iodide of potassa, fifty 

 grains to the ounce, added to the silver solution. 

 Cyanide of potassa may then be added, drop by 

 drop, tin the precipitate is dissolved, and the whole 

 filled up with four ounces of water. This solution 

 requires but a very few minutes' floating upon water 

 containing a small quantity of sulphuric acid ; and 

 it is then ready, after a bath of nitrate of silver, 

 for the camera, and will not present any of the dis- 

 agreeable spots so noticed by most photographers. 

 This paper Is probably the best for negative pic- 

 tures we have at present ; although. If very trans- 

 parent paper Is required, oiled paper may be used 

 for negative pictures very successfully ; or paper 

 varnished is equally good. The oiled paper may 

 be prepared as follows : Take the best walnut oil, 

 that oil having less tendency to darken paper of 

 any other kind, and oil it thoroughly. It must 



then be hung up in the light for a few days, the 

 longer the better, till quite dry. It may then be 

 iodized with the ammonlo-nltrate, the ammoniated 

 solution passing more readily over greased surfaces. 

 The varnished paper may be prepared by half an 

 ounce of mastic varnish and three ounces of spirits 

 of turpentine, hung up to dry, and treated as the 

 oiled paper in iodizing ; but both are better for 

 resting a short time previous to iodizing upon water 

 containing a little isinglass in solution, but used 

 very sparingly. 



As I have experienced the excellence of these 

 preparations, I hope they may be useful to your 

 photographic students. Weld Taylok. 



Bayswater. 



After-dilution of Solutions. — There are in gene- 

 ral use two methods of preparing sensitive paper. 

 In one, as in Mr. Talbot's, the iodide of silver is 

 formed in a state of purity, before being rendered , 

 sensitive : and as, for this end, a small quantity 

 only of nitrate of silver is necessary, a very dilute 

 solution will answer the purpose as well, or even 

 better, than a strong one ; but by the other method, 

 the paper being prepared with iodide of potassium 

 only, or with some other analogous salt, the iodide 

 of silver has to be formed by the same solution 

 that renders It sensitive. Now as for every 166*3 

 parts of iodide of potassium 170'1 parts of nitrate 

 of silver are required for this pui'pose, it Is evident 

 that a dilute solution could not be employed unless 

 a very large bulk were taken, and the paper kept 

 In a considerable time. 



The after-washing Is to remove from the surface 

 of the paper the great excess of silver, which is of 

 but little service, and prevents the paper from 

 keeping. William Crookes. 



Hammersmith. 



Stereoscopic Pictures from one Camera. — Your 

 correspondent Ramus will easily obtain stereo- 

 scopic pictures by either of the following plans : — 

 After the first picture Is taken, move the subject, 

 as on a pivot, either to the right or left, through 

 an angle of about 15° ; then take the second im- 

 pression : this will do very well for an inanimate 

 object, as a statue ; but, if a portrait Is required, 

 the camera, after taking the first picture, must be 

 moved either to the right or left, a distance of not 

 more than one-fifth of the distance It stands from 

 the sitter ; that Is, if the camera Is twenty feet 

 from the face of the sitter, the distance between 

 its first and second position should not exceed 

 four feet, otherwise the picture will appear dis- 

 torted, and the stereosity unnaturally great. Of 

 course it is absolutely necessary in this plan that 

 the sitter do not move his position between the 

 taking of the two impressions, and also that the 

 distance between him and the camera be the same 

 in both operations. 



