582 



NOTES AND QUERIES. 



[No. 189. 



The time to leave the positive in the fixing bath 

 varies from one hour to twelve. To get good 

 black and white tints, the average time is five or 

 six hours. When the desired tint is obtained, re- 

 move it into a bath composed of 



Water - - - - 6 oz. 

 Hypo. - - - - 1 oz. 



Leave in this for half an hour, and then keep it 

 in running water for several hours. If the water 

 is hot, the time of soaking may be lessened : boiling 

 water is objectionable. Nearly dry the positive 

 between sheets of clean blotting-paper, and finish 

 it by passing a very hot iron over it. 



General ]iema?-ks. — The albumenised paper will 

 keep any length of time in a dry place. 



When made sensitive, as directed, it will keep 

 three days, always supposing that it is both pre- 

 pared and kept most carefully excluded from white 

 light. If, instead of a solution of nitrate of silver 

 of ninety grains to the ounce, a weaker one be used, 

 to make the paper sensitive, it will keep when sen- 

 sitive a much longer time, — with a thirty-grain 

 solution, a fortnight, or sometimes even a month ; 

 but then it does not give a positive of the same 

 force and tone as that obtained with the stronger 

 solution. 



After the fixing bath has done its day's work, it 

 should be poured back into the bottle from which 

 it came, and the bottle be filled up from the finish- 

 ing bath ; and so the bath is kept always of the 

 same quantity ; and by adding from time to time 

 chloride of gold, it is kept of the same quality. 



The nitrate of silver and chloride of silver will 

 never have to be renewed. The iodide of silver 

 should be added as at first, viz. ten drops for about 

 every two hundred positives fixed ; and the acetic 

 acid, viz. two drops for about every four hundred. 



In a bath of twenty-four ounces, as many as 

 thirty positives, five inches by four, may be placed 

 at one time: but the dark tints will then appear 

 very slowly and gradually. 



To insure a good positive, next to having a good 

 negative, it is most important to print of the right 

 depth, neither too much nor too little. Great atten- 

 tion should be paid to this : for the finest tints are 

 only to be obtained in positives exposed exactly 

 the right time. 



Positives printed in a bright sun quickly are 

 always better than those obtained by longer ex- 

 posure without sun. H. P. 



21. Maddox Street, Regent Street. 



Test for Lenses. — In applying the methods re- 

 commended in your last Number for the purpose 

 of testing lenses, there is one precaution absolutely 

 necessary to be taken, but which all your corre- 

 spondents have omitted to point out. Tlie opera- 

 tor must take care that his focussing-glass is placed 

 at precisely the same distance from the lens as the 



collodionised glass is. To insure this, my practice 

 is to place a piece of ground glass in the dark 

 frame, which is afterwards to receive the collo- 

 dionised glass, and to obtain the focus of the lens 

 on that ; tlien to put in the proposed plate, and 

 obtain an impression as described by Me. Shad- 

 bolt. In this way I secure myself from what I 

 believe is often a source of fallacy in these experi- 

 ments, and am sure that I give the lens a fair 

 trial. E. S. 



Washing Collodion Pictures. — I have never 

 offered to your readers an opinion in photography 

 without having hona fide tested it, to the best of 

 my ability ; and however correct my friend Ma. 

 Shadbolt may be, chemically and theoretically, 

 I am convinced that in practice so good a tone is 

 never obtained in a positive collodion picture 

 which has been washed, as in one which has been 

 instantly fixed with the old saturated solution of 

 hyposulphite of soda. The unpleasant tints ob- 

 tained upon positive collodion pictures, I believe 

 to be much dependent upon the frequent washings 

 in the proofs. When a collodion picture is pro- 

 perly treated, it surpasses in pleasing effect every 

 other photograph. H. W. Diamond. 



MepTteiS to jaStiior €iuttiz&. 



Cremonas (Vol. vii., p. 501.). — A discriminative 

 account of the violins and basses by the great 

 Italian makers, showing, in every ascertainable 

 instance, the date of manufacture, and thereby 

 forming to some extent a chronological catalogue, 

 as it were, of the works of each master, would be, 

 indeed, a curious and interesting achievement. 

 Such a task, involving much consultation of books 

 and examination of instruments, calls for sounder 

 eye-sight and larger opportunities than are pos- 

 sessed by me ; but I shall rejoice if the desire ex- 

 pressed by your correspondent H. C. K. shall be 

 found to have stirred up some competent investi- 

 gator. Time and accident are gradually attaching, 

 to the fine instruments in question, a kind of 

 sibylline intensity of value ; and the inquiry, if 

 omitted now, may become impossible hereafter. 

 Let us not fear, however, that those " cunning'st 

 patterns of excelling art," the Amati, Stradivari, 

 and Guarneri fiddles, will eventually periS^i without 

 worthy issue, and " die, and leave the world no 

 copy." Provision to the contrary, it seems, has 

 already been made ; Monsieur Vuillaume " has 

 ta'en order for't," that is to say, if his instruments, 

 which at present look very like faithful fac-similes 

 of the renowned classic prototypes, shall verify 

 the confident predictions of their admirers, by 

 continuing to stand the test of time. 



My authority for 1664 as the date of birth of 

 Antonio Stradivari, is a living Belgian writer, 

 Monsieur Fetis, who has not stated from whence 



