NATURAL PHILOSOPHY. 137 



An instrument, invented and patented by Mr. Jolin E. Grisdale, 

 is capable of washing a full charge of prints in twenty minutes, 

 and that so jjerfectly, that at the end of this time some ordinaiy tests 

 for hyposulphite of soda fail to indicate its presence. " My inven- 

 tion," lie saj^s, "relates to a peculiar construction and arrange- 

 ment of centrifugal machinery or apparatus for washing photo- 

 graphic prints, and consists, according to one ai'rangement, in the 

 employment of a peculiarly-constructed revolving drum in comlji- 

 nation with a trough, in which such drum is partially immersed. 

 The prints to be washed are taken from the Avater in which they 

 have been placed on their removal from the fixing or other bath, 

 and are packed in one or more piles, which piles are jjlaced round 

 the circumference of the drum, each pile being composed of alter- 

 nate prints and sheets of wire gauze, or other open or reticulated 

 fabric, so that no two prints shall be in contact with each other. 

 These piles ai-e held in their places on the drum by means of open 

 frames or gratings, which bear against the opposite surfaces of 

 each pile, and are secured to the arms of the drum by screws or 

 otherwise, the whole or a portion of such frames or gratings form- 

 ing a i^art of the drum itself. Or, according to another arrange- 

 ment, the piles above described may be laid ilat upon a disk, which 

 is made to revolve either vertically or horizontally in a trough or 

 cistern, provision being made in the horizontal arrangement for 

 allowing the piles to be brouglit in or out of contact with the wa- 

 ter as required ; or, in lieu of the jjliotographic prints' being dis- 

 posed in the form of piles or packs round a drum or revolving disk, 

 they may be laid separately and individually round the surface of 

 a drum, a webbing of oi^en or reticulated faljric being wound on 

 such drum simultaneously with the placing of the prints thereon, 

 so as to inteqiose a thickness of the fabric between each succeed- 

 ing layer of prints. The process of washing consists in alternately 

 driving out the moisture from tlie prints by the centrifugal action 

 of the revolving' drum or disk, and saturating the prints again. 

 During the first part of the process, the prints are not immersed ; 

 but when the second part of the process, namely, the saturation, is 

 to be effected, the trough or cistern is to be supplied with water; 

 or the prints may be brought down into the water, and caused to 

 revolve therein and thoroughly saturated, when the water may be 

 run off from the trough again, or the drum or disk elevated, and 

 the moisture expelled by centrifugal force as before." 



Freshly-supplied water is forced through every pore of the 

 prints, the consequence being the elimination of every trace of 

 hyposulphite of soda in a very brief space of time, — British Jour- 

 nal of Photography. 



PHOTO-LITHOGRAPHY "WITH HALF-TONE. 



The production of printing surfaces on stone, zinc, etc., by the 

 agency of photography, has occupied the attention of experimen- 

 talists for many years ; and, in many respects, a high degree of 

 success has been obtained. The process of Mr. Osljorne, for the 

 woi'king of which a company has recently been formed in Amer- 

 12* 



