PROCEEDINGS OF THE SOCIETY. 119 



right for a few minutes ; to have to work by the hour over an instru- 

 ment so placed would become very distressing. It was a very pretty 

 way of mounting and keeping the specimens ; but metals such as iron 

 and steel were very apt to rust on the polished surface, and so ibe- 

 come spoilt, and he thought this method of keeping them would not 

 obviate this risk, so that it would be necessary to keep them in a 

 desiccator to prevent rusting, unless the surface was varnished, which 

 would necessitate cleaning off when it was desired to examine them. 

 He wished to express his interest in and appreciation of the apparatus 

 which Mr. Stead had brought before the Society, and to thank him for 

 having done so. 



Mr. J. W. Gordon said he had been extremely interested in the 

 subject of this paper, but with regard to one point mentioned by Mr. 

 Rosenhain, he thought they need not be dependent upon the cardboard- 

 box maker for a special shape to enable the Microscope to be used in an 

 inclined position, because a little seccotine would stick the pill-box to an 

 ordinary Microscope slip, which could be held in position by the clips 

 on the stage, and would enable the instrument to be used at any angle. 

 He thought the method of using a silvered mirror covering half the 

 aperture "would result incidentally in producing oblique illumination ; 

 and with regard to the method proposed by Mr. Stead of producing 

 oblique lighting, namely, by exposing the lamp without the mirror, it 

 appeared to him that this would limit the oblique lighting to one 

 particular angle. For that reason he wished to suggest for Mr. Stead's 

 consideration whether it would not be better to reflect the lamp light by 

 means of a small mirror which could be moved in any direction re- 

 quired, and so throw the light under any desired angle upon the object. 

 He desired to associate himself with the thanks to the author of the 

 paper to which Mr. Rosenhain had given expression. 



Mr. Stead, in reply, said he thought the result of using this Micro- 

 scope by manufacturers was likely to be the opposite of that feared by Mr. 

 Rosenhain : for when they began to appreciate elementary things, they 

 would not be likely to remain long contented with them, but would want 

 to possess what would afford them still greater advantages— an instance 

 of this had, in fact, only lately occurred. As regarded cut sections of 

 metal, such as steel shafts, etc., after they had been turned up and 

 polished in the machine shops they were really cut sections, and the 

 structure of the metal could be examined nearly as well with the aid oi 

 the portable Microscope as on sections cut out of them and brought into 

 the laboratory for examination in the usual way. Of course they could 

 not destroy shafts by cutting such pieces from the finished work. 

 Unfortunately, iron and steel did rust if exposed to damp atmosphere, 

 but after examining them, a drop of suitable varnish on the surface pro- 

 tected the polished and etched surfaces. If the sections were properly 

 prepared, and heated to about 100° C, and then were placed into tubes 

 and packed close with dry cotton-wool, rusting was prevented, and 

 this alternative method was most useful. Varnish, howe\ er, was usually 

 quite sufficient for the purpose, but in course of time the surfaces under 

 the varnish sometimes became dull, but not rusty. In such cases the 

 varnish could be removed by a suitable solvent, and the surfaces re- 

 polished and etched. As regarded oblique illumination, he intended to 



