Silver Haloid Molecule by Mechanical Force. 47 



tion does not exist, and that as all forms of energy have been 

 shown in the previous papers of this series to be capable of 

 impressing an invisible image, so also with stronger manifes- 

 tations, any form of energy is capable of disrupting the mole- 

 cule. 



I was able to show many years ago that mechanical force 

 could produce a latent image. Lines drawn with a glass 

 rod on a sensitive surface could be rendered visible by develop- 

 ment in the same way as impressions of light. An embossed 

 card pressed on a sensitive film left an invisible image, which 

 could be brought out by a reducing agent. The raised 

 portions of the embossed work exerted a stronger pressure on 

 the sensitive film than the rest of the card, and these portions 

 darkened when acted upon by a reducing agent. In the same 

 way, the lines traced with a glass rod blackened under a 

 developer. In each case, it was the portions which had been 

 subjected to pressure which yielded first to the reducer. It 

 was therefore clear that in the molecules which had received 

 this slight pressure the affinities of the atoms had been 

 loosened. 



To bring these phenomena fully into line with the others, 

 it is now necessary to prove that an increased pressure can 

 take the place of a reducing agent, and disrupt the melecule. 

 And this is actually the case. 



It was found that the breaking up could be produced in 

 two ways— by simple pressure and by shearing stress. Silver 

 chloride and bromide formed and washed in absence of active 

 light were subjected to these agencies. 



1. Simple Pressure. — In the first trial made with silver 

 chloride it was enclosed in asbestos paper, which had been 

 first ignited with a blast lamp to remove all traces of organic 

 matter present. This method was tried in order that the 

 chloride should be in contact with perfectly inactive material 

 only, but it was not found to answer. The great pressure 

 employed forced the dry chloride into the pores of the paper, 

 cementing it together, so that the opposite sides could not be 

 separated. Platinum foil was then substituted with satisfac- 

 tory results. With a pressure of about one hundred thousand 

 pounds to the square inch, maintained for twenty-four hours, 

 the chloride was completely blackened, except at the edges, 

 where, owing to greater thinness, the pressure was less. Very 

 bright foil was used in order to detect the slightest discoloration 

 that might occur, but none resulted : it was impossible to 

 distinguish the portions which had been in contact with the 

 darkened chloride from those that had not. The chloride did 



