444 



NOTES AND QUERIES. 



[No. 158. 



purple colour, owing partly to the union of tbe 

 iodine with the starch in the paper, and will keep 

 good any length of time. 



The solution for rendering these Iodized sheets 

 sensitive consists of 



Nitrate of silver - 

 Glacial acetic acid 

 Water 



15 grains. 

 15 „ 

 1 ounce. 



The marked side of the paper is to be laid care- 

 fully on this solution, and kept there for about 

 half a minute longer than Is necessary to com- 

 pletely decolorise it (from seven to ten minutes), 

 and then floated on distilled water for a few 

 minutes. It must then be dried between blotting- 

 paper, and kept in perfect darkness in a portfolio 

 until required. With only one washing in distilled 

 water, as above, it will not keep good longer than 

 six days ; but If washed sufficiently It will keep 

 good for weeks. 



It is hardly possible to state any definite time 

 for the exposure In the camera, as this of course 

 must vary with the intensity of light ; but with a 

 lens of twelve inches focal length, with a half-inch 

 aperture in front of it, from one to two minutes 

 will suffice on a bright day with the sun out ; while 

 on a dark gloomy day, from seven to ten minutes 

 may be requisite. 



For developing the picture, I employ four parts 

 of a nearly saturated solution of gallic add, and 

 one part of the solution previously employed for 

 exciting the paper ; these are to be well mixed, and 

 the marked side of the paper floated on it. The 

 picture will soon begin to appear, and should be 

 completely out In less than an hour, and before 

 the gallo-nltrate Is decomposed ; It must then be 

 washed, soaked in tolerably strong hyposulphite 

 of soda until all the yellow iodide is removed, 

 washed again several times, and then dried, and 

 either Ironed over, or held before a fire to melt the 

 wax. The greatest care must be taken to have 

 the dish perfectly clean to contain the gallo-nitrate ; 

 it ought to be rubbed with strong nitric acid every 

 now and then, to remove the stains from a pre- 

 vious operation : unless this precaution be taken 

 to avoid the presence of dirt, the picture will be 

 covered with stains similar to marbling in book- 

 binding. The gallic acid and nitrate of silver 

 must also be filtered before mixing. 



By adhering to these directions, any person who 

 has had a little experience in manipulation may 

 make sure of getting excellent results, with a far 

 less number of failures than by any other process. 

 I have endeavoured to state everything as explicitly 

 as possible, but should I not have rendered myself 

 sufficiently intelligible in any part of the process, 

 I shall be happy to give any information that lays 

 in my power. William Ceookes. 



Hammersmith. 



P. S. — I have seen several inquiries respecting 

 the price that ought to be paid for a good lens, 

 the general idea seeming to be that they are very 

 expensive. The lens I always employ cost me 

 fifteen shillings ; it was made at Slater's, and is^ 

 l^r inch in diameter, and 12 inch focus. The pic- 

 ture I forward as an illustration of the process 

 will show what can be done with it : It was taken 

 In one minute with a half-Inch aperture in front 

 of the lens. 



[We have to thank our Correspondent for a very 

 admirable specimen of his skill. We can assure our 

 readers that it affords the best evidence of the value 

 and practicability of the process which Mr. Crookes 

 has so kindly communicated. — Ed.] 



ISiefHitS ta Minav ^uttitS, 



Oblations (Vol. vi., p. 316.). — I could supply 

 W. E. with plenty of instances such as he wishes 

 to find. Some of them are given In How shall ws 

 conform to the Liturgy? 2d ed. p. 208, J. C. R. 



The Larch (Vol. vi., p. 350.). — Your correspon- 

 dent's reference to Vol. vl., p. 276. Is incorrect : It 

 should be p. 269. I copied your correspondent's 

 Query, and sent it to the Editor of the Gardener s 

 Chronicle^ and in the Number for October 23rd 

 (p. 676. col. 2.) he replies : 



" We cannot for our own parts add anything to what 

 we have stated upon this subject on former occasions; 

 but we undertake to say that the dictum in question 

 does not belonpf to the nobleman whose name has been 

 thus introduced, if it has any parentage whatever. On 

 the contrary, we have good reason to know that Lord 

 Portman entertains no opinion of the kind. What our 

 own views are, will be found at p. 435. of our volume 

 for 1851." 



To the Gardener's Chronicle for 1851, p. 435., I 

 would refer your correspondent; and for some- 

 thing like the dictum which he attributes to Lord 

 Portman, I would refer him to the Journal of the 

 Royal Agricidtwal Society of England, vol. ix. 

 p. 372., where he will find it asserted by Sir J. S. 

 Menteath, not " that the larch fails except on," 

 but " the larch grows naturally only on " the 

 primitive mountains. George E. Frere. 



The Chain of Salvation (Vol. vi., p. 268.).— 

 Your correspondent E. N. does not seem to be 

 aware that this Chain is only a transcript of part 

 of the engraved title-page to WoUebius's Christian 

 Divinity, translated by Alexander Ross (of volu- 

 minous memory) : London, 1650, r2mo. Instead 

 of " sanctified," after Avhich your correspondent 

 places a mark of interrogation, the original has 

 more properly "testified." In other respects it 

 Is the same as in his manuscript. Nothing Is 

 more common amongst the writers of theological 

 " abridgments " and " marrows " of the time of 



