and on certain Appliances for Illumination. 115 



of Gray and Selby, opticians, Nottingham, wlio will be happy to 

 make similar apparatus upon my patterns at a reasonable cost. 

 I shall be glad to render my humble and friendly assistance to 

 anyone who may desire to test the utility of these aids to practical 

 microscopic work. 



Sub-stage : — D, position of one of the diaphragms when in U33. S, catch- 

 spring. B, bar, sliding up or down by a fork F, which is held by the bevellel 

 edges of the fixed piece H. T, short tube by which the stage is attache:! to the 

 microscope. 



Nottingham, Aug. 11, 1873. 



