Sept. 29. 1855.] 



NOTES AND QUERIES. 



251 



. the end the water always will form a limpid solution with 

 the nitrate of silver, and is altogether as good as distilled 

 •water.' It is this which M. Disderi calls preparation of 

 distilled water without an alembic. Without reference to 

 the title, I believe that M. Disderi is perfectly right, and 

 the photographers who have a horror of a turbid bath can 

 follow this method. Chloride of silver, contrarj' to iodide 

 of silver, is completely insoluble iu nitrate of silver, how- 

 ever concentrated it may be, when the salt of silver is 

 neuter; but a few drops of acetic acid added to a turbid 

 bath render it as limpid as if distilled water had been 

 employed. 



" A bath rendered clear by acetic acid is excellent for 

 positive paper, and it is necessary in the case of negative 

 papers, that the silver bath should be acidulated with 

 acetic acid ; the acetic acid therefore becomes the means 

 of rendering the bath of nitrate of silver clear, notwith- 

 standing conmion water may have been used. 



" In photography on paper it appears to me evident, 

 that the employment of distilled water is superfluous. 



'• For collodion negatives, in the case of portraits, we en- 

 deavour to obtain the greatest degree of sensitiveness, and 

 one of the most efficacious means is to use fused nitrate 

 of silver, that is to say, nitrate of silver as neutral as pos- 

 sible; consequently the addition of acetic acid to clear 

 the bath rendered turbid by the chloride of silver in suspen- 

 sion injures its sensitiveness. In this case you must use 

 •water freed from chlorides by the process ofM. Disde'ri. 



" Suppose a plate to be sensitized in a bath rendered 

 milky bj' the use of common water, it is certain that the 

 chloride in suspension can only increase its sensibility; 

 for success in photography depends precisely on the com- 

 bination of several different powerful photogenic sub- 

 stances, all tending to the same result. 



" Moreover, the acetic and pyrogallic acid would render 

 the solution clear, even before the commencement of the 

 reduction of the silver. And if it remains turbid after 

 the addition of pyrogallic acid, one may be quite sure 

 that it is the iodide precipitated which has caused it, and 

 not the chloride pre-existing in suspension, and which 

 will have dissolved by means of the acid. Consequently, 

 in the presence of the acids, the slight precipitate pro- 

 duced by common water will have always disappeared 

 before the appearance of the image; and the collodion 

 will not, any more than the paper, retain the least trace 

 of the chloride in the state of a precipitate. 



"The employmentof distilled water itself, and rain-water, 

 which nearly resembles it, often causes a failure in work- j 

 ing with collodion, in consequence of its not being pure. ; 

 Distilled water that one purchases, is often produced by 

 the condensation of the steam issuing from the cylinders j 

 of steam-engines. This is always contaminated with ; 

 organic matter, resulting from the decomposition of the 

 oils used for lubricating the piston. When this is em- 

 ployed in the preparation of terchloride of gold, or the 

 silver and pyrogallic acid baths, the silver and gold are 

 reduced, and the operations fail, liain-water, which has 

 run over all the impurities on the roofs, produces an analo- 

 gous effect. Drinking-water is, therefore, far preferable ; 

 one is always more certain of its quality. 



" It is a very common opinion, that filtered water pos- 

 sesses superior qualities ; if they are equally clear, com- 

 mon water is precisely the same: the fifter can only 

 retain the matters in suspension, and can in no wav change 

 the nature or the quantity of the salts in solution. These 

 saline substances can ha-v-e no injurious effect on paper or 

 collodion, as I have just shown. If the collodion exhibits 

 a saline deposit, one may be certain that it proceeds from 

 imperfect washing. It is only the final Avashing of pho- 

 tographs on silver or collodion that requires very pure 

 distilled water. The washing of photographs on silver, 



No. 309 ] 



j even, may be finished with common water, by rapidly 

 ' evaporating the water on the surface. It will not fail to 

 ; produce a saline deposit, but its continuity renders it in- 

 divisible; it is like a new varnish, which adds to the 

 solidity of the picture and enriches its tones. 



" In certain localities, however, if the last washing is not 

 made with distilled water, stains are apt to be produced 

 on vigorous pictures. I have found this to be the case in 

 the mountainous district of the Department du Gard, but 

 without being able to ascertain exactlj' the cause ; there 

 is no deposit, but a marbling of a bluish colour, caused, 

 no doubt, by some combination of sulphur. When the 

 water contains saline substances, it moistens the plate 

 easily, whilst distilled water divides itself into small 

 streams with the slightest heat. The water of the De- 

 partment du Gard behaves in this respect like distilled 

 water ; but, on evaporation, there is a chemical action 

 from some of its constituents upon the silver. 



" In fine, I consider the employment of distilled ■water in 

 photography to be a mania which sooner or later will 

 pass away, except in the few cases which I have indicated." 



M. A. Gaudin. 



Single Stereoscopic Pictures. — The communication 

 which I made to "N. & Q.," Vol. xii., p. 171., containing 

 some suggestions for obtaining single stereoscopic pic-, 

 tures, has called forth a reply from a Mr. C. Mansfikld 

 Ingleby, of Birmingham, which I should not have 

 troubled myself to notice, had it not contained assertions 

 which, if left uncontradicted, might deter unprejudiced 

 persons from trj'ing the experiment. 



The statement is to this effect, that no stereoscopic 

 picture can be produced, unless two views be taken, and 

 the same be viewed through a binocular apparatus, and 

 that to get a single stereoscopic picture is simply impos- 

 sible ; and farther, that the method suggested in my 

 communication is a pure delusion. 



To this I must say, that had Mil. C. Mansfield In- 

 gleby taken the trouble to try the experiment as de- 

 scribed, he would in a moment have seen that a stereo- 

 scopic picture could he produced by the method, and that 

 to a surprising extent, even with the imperfect apparatus 

 described. From the remarks of Mk. Ingleby one 

 would infer that he has thoroughly studied the theory of 

 the stereoscope. If this is really the case, he has done so 

 without much benefit, otherwise he would not so posi- 

 tively' have denied a fact so easil}' verified, provided he 

 had been gifted Avith ordinary healthy vision, and had 

 no prejudice in the matter. If communications on sub- 

 jects so little understood (as the best method of taking 

 stereoscopic pictures appears to be), are to be ridiculed in 

 this style (which Mr. Mansfield Ingleby has thought 

 proper to adopt), it will certainly be the means of deterring 

 those from giving hints (however crude they may be), 

 which might afterwards, in experienced hands, lead to 

 important results. Geo. Noejian. 



Hull. 



Ancient Cements (Vol. xii., p. 185.). — Will it be 

 of any service to Mr. E.. J. Allen to consult 

 Weale's small treatises on The Art of Making 

 Foundations, Concrete Works, ^c, and On Limes, 

 Cements, Mortars, S^c. ? If these are of too rudi- 

 mentary a character, there are treatises by Vicat, 

 Smeaton, Pasley, and papers read before the 



