8-4 J. Wafcerhouse — The Application df Photo yrapliy [No. 2, 



the printing fraiiiu iind passed through a lithographic press in contact with 

 a polished stone, or zinc plate, which has been coated with a lithographic 

 transfer ink, and thus receives an even coat of the greasy ink. The 

 inked print is immersed for a few minutes in tepid water, to soften the 

 gelatine still remaining soluble in the parts not acted on by light, and then 

 laid on a sloping glass or metal plate and gently washed with a sponge 

 and warm water till all the unaltered gelatine is removed, carrying the 

 superfluous ink with it. The lines, on which the light has acted, remain 

 insoluble and retain the ink, forming a clear image of the subject in a 

 greasy transfer ink, precisely similar to the ordinary lithographic transfer 

 drawing. When all the details are clearly and sharply defined, and the 

 ground is quite free from ink, the print is rinsed in clean water and dried. 

 It is then ready for transfer to stone or zinc. 



It often happens that a map is too large to be photographed in a single 

 section. In this case the transfer prints of the different negatives are 

 carefully joined together with gelatine and transferred to the stone or plate ; 

 or if too large to be printed in one sheet, the joined-up transfers may be cut 

 \x]y into as many convenient- sized sections as may be necessary. 



Zinc plates possess great advantages over lithographic stones on 

 account of their superior lightness, cheapness, facility for storage and less 

 liability to breakage, and are therefore to be preferred in reproducing plans 

 of large size. For fine work stone is considered by some to give better 

 results than zinc, but I believe that if due care be taken as good prints 

 may be made from zinc as the best from stone. 



The plates used for this purpose are about -f-Q of an inch in thickness, 

 and have one side carefully planed and smoothed ; but in order to give a 

 somewhat porous surface to the plate, so that it may be more absorbent of 

 moisture and hold the greasy ink better, the planed side of the plate is 

 grained, or roughened by grinding it evenly all over with very fine sand and 

 water. After the transfers are made, the plate is etched with a preparation 

 of gum and decoction of gall-nuts to which a little phosphoric acid is 

 added. 



If the transfers are made to a lithographic stone instead of to a zinc 

 plate, the operations are exactly the same as for transferring an ordinary 

 lithographic transfer-drawing, except that the stone need not be heated. 

 The operations of printing, whether from zinc or from stone, are precisely 

 the same as in ordinary lithography. 



Various modifications have been introduced, but the above process is 

 still one of the best and most simple, and, if care be taken with suitable 

 subjects, results may be obtained by it not to be surpassed by any other 

 method. Full details regarding it will be found in Sir H. James' 

 ' Photoz incoijraphy ,' also in the Fhotoyraphic JS'eivs, Vol. XII, page 



