Feb. 3. 1855.] 



NOTES AND QUERIES. 



91 



shades, but next, that otherwise, with the utmost care 

 possible, I cannot help getting one part of the plate more 

 sensitive than the other, by the syrup washing the nitrate 

 more from the side on which it is first poured on, than 

 from that on which it runs off. It is evident, however, 

 that after a certain time Mr. Shadbolt's syrup will be- 

 come sufficiently nitrated b^' what it will wash off from 

 the plate, and this nitrate will not, as he says, all preci- 

 pitate by exposure to light, but a considerable portion 

 •will always remain in combination. My object is to pre- 

 vent the washing off by having the syrup and the wash- 

 ing bath each about equally charged with nitrate ; and 

 this small excess of nitrate does not injure the solution 

 of grape sugar so much as it will most samples of honey, 

 as the uucrystallisable sugar which the latter contains 

 generally decomposes and causes the plate to fog. 



Now for the other portion of his statement : that I have 

 taken his process, merely interpolating mine for making 

 grape sugar. In my letter I said that I adopted tlie plan of 

 Mk. Siiadbolt in washing the plate, which was excellent ; 

 and as that makes the essential difference between his 

 process and mine, I felt that in so saying I had given him 

 all his due. And then I gave a process in which, for 

 reasons before stated, I used grape sugar, not honey, and 

 put nitrate of silver in the sj-rup ; and these differences 

 being certainlj' at least as great as those between Mr. 

 Shadbolt's process and mine, I leave it to the public to 

 decide whether he has behaved as justly to me as I have 

 to him. 



I may add also, in answer to what he saj's of the in- 

 finitesimal nature of my dose of nitrate, that to all ac- 

 quainted with the chemistry of photography it is well 

 known what is the comportment of iodide of silver in the 

 presence of even the smallest excess of nitrate of silver, 

 and of the same substance when nitrate is not present. 

 I feel the utmost confidence that my plan will be the one 

 ultimately adopted for preserving the plates, as by this 

 method with the grape sugar the results must be much 

 more certain and regular than when honey, a substance 

 •which is of so uncertain a constitution, is employed. In 

 conclusion, I may add that I am very sorry to have tres- 

 passed on your pages for so long a space; but as you 

 have given publication to Mr. Shadbolt's letter, I hope 

 you will permit me, with your usual kindness, to make 

 my response to it, and I promise that I will not trouble 

 you farther on this matter ; for should any reply be 

 made to this letter, having now fully stated my case, and 

 being also at present in a foreign country, I shall leave it 

 to your readers to decide ■\vhether Mr. Shadbolt or my- 

 self is in the right, and feel no doubt as to the result. 



r. Maxwell Lyte. 



Maison George, Rue Montpensier, Pau. 

 Jan. 19, 1855. 



Bromo-iodide of Silver. — Mr. Reade, in a letter he 

 addressed to you (Vol. xL, p. 51.), endeavours to show 

 that the statements I made in my former letter in refer- 

 ence to this subject are at variance with those of Mr. 

 Lttte, which is not the case. He says that I prove, or 

 think I prove, by my experiment, which he describes, 

 that the so-called bromo-iodide of silver (for such, he 

 says, is the precipitate I obtain from Dr. Diamond's 

 solution) is in fact nothing of the kind, but consists en- 

 tirelj' of iodide of silver; whereas, he says, Mr. Lyte 

 first of all proves that the same compound'and iodide of 

 silver when dissolved in strong liq. amm. are each simi- 

 larly acted upon by dilute nitric acid, and then forms a 

 true bromo-iodide of silver, but in such combination as to 

 exhibit the same kind of milkiness which occurs with 

 pure bromide of silver on the addition of an acid, and 

 hence leads to the conclusion that bromide and not iodide 

 of silver is exhibited by this experiment. 



Now I beg to remark, in the first place, thi^t the true 

 bromo-iodide of silver which Mr. Lyte forms by adding 

 an excess of nitrate of silver to a solution of the bromide 

 and iodide of potassium, consisting as it does of a mixture 

 of bromide with iodide of silver, is a very different com- 

 pound from Mr. Reade's bromo-iodide of silver ; and, 

 secondly, that my statement as to the latter being iodide 

 of silver, is confirmed by Mr. LrxE, although Mr. Reade 

 is endeavouring to prove the contrary. 



Again, Mr. Reade states that the whole of the silver 

 from a solution of the double bromide and double iodide 

 of silver is precipitated by water, which is quite true ; but 

 what it has to do with the question under discussion I 

 am St a loss to conceive. The whole of the silver from 

 Dr Diamond's solution is precipitated by water, but it 

 does not necessarily follow that the precipitate consists 

 either wholly or partly of bromide or bromo-iodide of 

 silver. On the contrary, the whole of the bromide of 

 silver is, as I stated in my former letter, decomposed by 

 the iodide of potassium, iodide of silver and bromide of 

 potassium being formed ; and if Mr. Reade will take 

 the trouble to test the precipitate for bromine, after hav- 

 ing well washed it with water, he will find that it does 

 not contain a trace of that element. 



Farther, Mr. Reade states that paper prepared •with 

 Dr. Diamond's solution is more sensitive than ordinary 

 calotype paper in the proportion of 10 to 1 ; but what 

 does Dr. Diamond himself say as to the effect of his so- 

 lution of bromide of silver? He says {Photog. Journal, 

 vol. 1. p. 132.) it does not increase the general sensitive- 

 ness of the paper, although it seems to accelerate its power 

 of receiving impressions from the green rays ; a statement 

 ■which, as far as regards the general sensitiveness of the 

 paper, is quite in accordance with my experience. 



In conclusion, if Mr. Reade will wash his paper more 

 thoroughly after applying the solution, so as to get rid of 

 the whole of the bromide and iodide of potassium, I am 

 confident he ■will not find it more sensitive than ordinary 

 calotype paper. J, Leachmak. 



20. Compton Terrace, Islington. 



3RepIte^ to Minat ^utvitS. 



Death-bed Superstition (Vol. xi., p. 7.). — An 

 extract from your paper, thus headed, having 

 been extensively copied, I beg to state that the 

 whole story is a misrepresentation, no doubt un- 

 intentional. I ■was the clergyman of Charlcombe 

 at the time alluded to, and no death took place in 

 the parish during the year 1852 ; but in 1850 the 

 clerk came to me to borrow, not the plate, for 

 there was none, but a pewter plate to place it on 

 the body of a person already dead, to prevent the 

 body swelling. It is true I used the plate as a 

 paten, but it was asked for simply because it was 

 pewter ; so that it might be a case of quackery, 

 but not of superstition ; and I think it is plain to 

 any one that a dying person could hardly bear a 

 pewter plate filled with salt upon his chest, and if 

 placed there it would be much more likely to 

 hasten death than to alleviate it. 



Ed.mund Ward Peahs. 



" Whychcotte of St. Johns" (Vol. iii., p. 302. ; 

 Vol. xi., p. 27.). — The authorship of this very 



