2 DAGUERREOTYPE 



friction with cotton nnd pumice ; avoiding to touch the pinto with the fingers, or with 

 the part of the cotton held in them, or to breathe upon the plate, since spots would 

 thereby be produced. After cleaning with cotton alone, the plate is ready for the next 

 operation. 



The second stage is that of iodising the plate. A box is prepared, having iodine 

 strewed over its bottom, and the silver plate, face downwards, is placed a few inches 

 above the iodine, and the lid of the box being closed, all is left at rest for a short 

 time. The plate must be left in this position till the surface of the silver acquires a 

 iine golden hue, caused by the vapours of the iodine rising and condensing upon it ; 

 but it should not be allowed to assume a violet tint. The room should bo darkened, 

 and no heat should be employed. When the box is in constant use it gets impreg- 

 nated with iodine, and acts more uniformly and rapidly ; but in general states of the 

 atmospheric temperature this operation will bo effected in about twenty minutes. If 

 the purple colour be produced, the plate must be repolished, and the whole process 

 repeated. 



The plate with its golden hue is to be introduced, with its frame, to the camera 

 obscura. During this transfer the light must not bo suffered to strike upon the 

 surface of the plate ; on which account, the camera obscura may be lighted briefly 

 with a small wax taper. 



The plate is now submitted to the third operation, that of the camera obscura, and 

 with the least possible delay. The action of the solar radiations is obviously quicker 

 the brighter the radiations which act upon it ; and the more correct, according as 

 the focus of the camera is previously accurately adjusted to the place of the plate, 

 by moving backwards and forwards a roughened pane of glass, till the focal point be 

 found ; and the plate is to bo inserted precisely there. This silver plate exactly re- 

 places the ground glass. While the prepared plate is being fastened, the camera must 

 be closed. The plate is now in a proper position to receive and retain the impression 

 of the image of the objects presented the moment that the camera is opened. Ex- 

 perience alone can teach the proper length of time for submitting the plate to the 

 concentrated rays of light ; because that time varies with the climate, the seasons, 

 and the time of day. More time should not be allowed to pass than what is necessary 

 for fixing a distinct impression, because the parts meant to be clear would be apt to 

 become clouded. The impression of the image of nature is now actually made upon the 

 plate ; but it is as yet invisible ; and it is only after a lapse of several minutes, during 

 which it is exposed to mercurial vapour, that faint tracings of the objects begin to be 

 seen. 



The fourth is the operation with quicksilver, which must follow as soon as possible 

 the completion of the third. Here a phial of quicksilver, a spirit-lamp, and a glass 

 funnel with a long neck, are required. The funnel is used for pouring the mercury 

 into a cup, placed in the bottom of an apparatus which will allow of the application 

 of heat. No daylight must be admitted to the mercury box, a small taper only being 

 used to examine, from time to time, the effects. The plate with the dormant image 

 is placed some distance above the mercury, which vaporising, evokes in a truly 

 magical manner, the delicate lines which the solar pencil has traced. 



After each operation, the interior of the apparatus and the black board or frame 

 should be carefully wiped, in order to remove every particle of mercury. The 

 picture may now bo inspected in a feeble light, to see how far the process has suc- 

 ceeded. The plate, freed from the metallic bands, is to be placed in a box, provided 

 with a cover and grooves, to exclude the light, till it is made to undergo the last 

 operation. For the fifth and last operation the following articles are now required : 

 strong brine, or a weak solution of hyposulphite of soda ; two troughs of tin plato, nnd 

 a jug of distilled water. The object of this process is to fix the photographic pii-t urc. 

 One of the troughs is to be filled with brine to the depth of an inch, and th< 

 with pure water, both liquids being heated somewhat under the boiling point. The 

 solution of hyposulphite of soda is preferable, and does not need to be warm. Tho 

 plato is to be first immersed in the pure water for a moment, and transferred imme- 

 diately to the saline solution, and moved to and fro in it to equalise the action of tho 

 liquor. Whenever the yellow tint of the iodine is removed, the plato is to bo liftr-i 

 out by the edges, and dipped straightway in the water-trough. The plato. when 

 lifted out of the water-trough, is to bo placed immediately on an inclined plane ; and 

 without allowing it time to dry, is to bo floated over with hot distilled water from tho 

 top, so as to carry off all the saline matter. As tho quicksilver which 1 races the i 

 will not bear touching, the silvered plate should be secured by a cover of glass, made 

 tight at the edges by pasting paper round them. 



The Daguerreotype process as thus published, although even then an excee*linp;ly 

 beautiful process, was not sufficiently sensitive to enable tho operator to obtain por. 

 traits from the life. A period of twenty minutes was required, oven with the most 



