274 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 40 



Swift's Mineral Microscope. — This extraordi- 

 nary instrument (fig. 40) was made by Messrs. 

 Swift and Son on the instructions and after the 

 design of an amateur who desired to have a Micro- 

 scope which would allow of the examination of 

 large pieces of mineral. The whole is of wood, 

 except the body-tube and stem. 



The stem carrying the body-tube is fixed to 



an inclined plate on which moves by rack and 



pinion a large stage. In this stage slides laterally 



a broad plate on which rotates a truncated disc 



with two uprights. The uprights have slots and 



clamp-screws for allowing yet another plate to be 



raised and lowered. In the last plate slides 



from back to front (by a slot and clamp-screw) 



a narrow plate with a high ledge at the lower 



end, the ledge and end of the plate being 



padded with wash-leather. In the uprights 



are sockets for two large wooden screws 



with spherical ends and indiarubber rings 



to hold the object. 



