1086 



ultra-microscope Reinders and Ha:mburger ') have investigated the 

 extremely thin metal and salt layers formed by vaporization. For 

 CaF^, vvhich was nsed in many of the following experiments, they 

 found the field optically empty. Also for tungsten layers the field 

 was optically empty, as well in the case that tungsten was conden- 

 sed directly on the wall, as when tlie tungsten particles stick 

 in a salt layer. With the ultra microscope there could thus 

 be found no difference between a lamp treated with salt and an 

 ordinary one. P'or metals with a lower melting-point as silver, the 

 molecules of which have a greater mobility, a difference was found. 

 A thin silver layer precipitated on glass showed ultramicroscopically 

 a close network of ultramicrons. When the silver is precipitated 

 upon a salt layer {CaF,) the field was found optically empty. The 

 presence of the salt prevents therefore the molecules from forming 

 conglomerates. They evidently lie dispersed through the salt, so 

 that the action of the latter is due to its keeping the metal mole- 

 cules separated. We have examined more closely the question, how 

 this influences the absorption of the light and investigated, whether 

 the optical behaviour of such a thin layer might be closely connected 

 with its electrical conductivity. For this purpose we iiave made a series 

 of measurements on the conductivity of these layers and really 

 found, that in a lamp with salt much more tungsten must be vapo- 

 rized before an electrically continuous layer is formed than in lamps 



100^ 



60 mm 



1) W. Reinders aud L. Hamburger, These Proceedings. 



