A Manual Of Photography

224 PRACTICE OF PHOTOGRAPHY. sensitive paper by two mere particles of wafer, the progress oI the operation may from time to time be observed, and stopped at the moment when the picture is finished. 19. It ought then, as soon as possible, to be soaked in warm water, and fixed in the manner described in § 14. 20. In these pictures there is a curious and beautiful variety in the tints of colour they will occasionally assume, varying from a rich golden orange to purple and black. This effect depends in a great degree upon the paper itself ; but it is modified con- siderably by the strength of the hyposulphite, the length of the time exposed to it, by the capacity of the paper to imbibe it, and partly, perhaps, * by the nature of the light. Warm sepia- coloured pictures may generally be obtained by drying the paper, by pressure, and making it imbibe the hyposulphite supplied in liberal quantity. The paper of " I. Whatman, Turkey Mill,” seems to give pictures of the finest colour, and, upon tlie whole, to answer best for the purpose. If the chemical agents employed be pure, the operator, who keeps in view tlie intention of each separate process, and either adopting the manipulation recommended, or improving upon it from his own resources, may rely with confidence upon a satis- factory result. This calotype paper is so exceedingly sensitive to the influence of light, that very beautiful photogenic copies of lace, feathers, leaves, and such like articles, may be made by the light of a common coal-gas flame, or an Argand lamp. The mode of proceeding is precisely that described for obtaining the ordinary photogenic drawings by daylight, only substituting tlie calotype paper, which should be damp, for the common photogenic. "When exposing tlie prepared paper to the light, it should be held about four or five inches from the flame, and tlie time required will be about three minutes. Section II.—Modified Processes. But little remains to be added to this very clear and satisfac- tory description of the Talbotype process,—to which, indeed, is mainly due the perfection to which it has arrived both at home and abroad. There are, however, a few modifications which must be noticed, as tending to simplify the details in some cases, and to improve the general effects in others. In the main, however, it will be