PROCEEDINGS OF THE SOCIETY. 379 s ' 



an achromatic projection lens ; the whole being fitted upon a mahogany 

 base capable of being tilted. 



The usual heating coil of the Nernst lamp had been removed and 1 

 the filament was heated by the temporary application of the flame of a 

 spirit-lamp, the carrier of the electric lamp being so arranged that the 

 spirit-lamp could be applied when required, and the opening closed when 

 necessary. The lamp was also fitted with centring screws to enable the^ 

 filament to be brought into the optic axis. The whole of the optical 

 bench could be readily moved by means of a tangent screw, enabling any 

 part of the spectrum to be brought into the field of the Microscope. 



In setting up the apparatus it had been found most convenient to 

 bring the adjustable slit and the electric light into the optic axis of the 

 Microscope by viewing the images of these through the substage con- 

 denser, the prism, &c. could then be put into position, and by focussing 

 the light by means of the aplanatic bull's eye a brilliant beam could be 

 directed upon the slit. It had also been of advantage to have a small 

 slit a few inches from the substage, as a sharp image of the spectrum 

 could then be projected on to this. The diatoms shown by this method' 

 of illumination under a high-power apochromatic objective exhibited the- 

 markings with exceptional sharpness of definition, which elicited high 

 commendation from those who examined them. 



The thanks of the Society were voted to Mr. Curties for his exhibit, 

 and explanation. 



Messrs. W. Watson & Sons exhibited a new form of Museum Micro- 

 scope fitted inside a locked glass case through which the eye-piece tube 

 projects. The circular stage contains 12 objects and can be rotated from 

 the outside of case. 



A projecting milled head provides the 'means of focussing, the 

 arrangement of the latter being such that all danger to object or objec- 

 tive by an unskilled observer is avoided.' 



The instrument is intended for use with low powers — and a polari- 

 scope attachment can also be fitted. 



Messrs. Watson also exhibited a simple form of Stand Condenser of 

 long focus, furnished with an iris diaphragm, also adjustments to the 

 horizontal and vertical movements. 



The President thought that the small Microscope for museum use, 

 exhibited by Messrs. Watson & Sons, was an extremely useful arrange- 

 ment for the purpose, resembling a similar form of instrument which had 

 been adopted at the Smithsonian Museum at Washington. The object 

 of this contrivance was to enable even children to see microscopic objects 

 without handling them, and he thought if it was introduced to the 

 notice of the directors of museums here it would be sure to " take on." 

 There was at the Natural History Museum an arrangement by which 

 certain Foraminifera could be seen magnified by a lens, but this was so 

 placed as to be in a rather uncomfortable position to look through, and 

 certainly in no way comparable for convenience with the one now before 

 them, by which a dozen objects could be viewed in succession. Of course 

 there was a great difference between the conditions at the Washington 

 Museum, where perhaps only a few dozen people passed through in the 



