In using the mechanical stage, it should first be 

 determined how many spaces, or how much of one space 

 is contained within the limits of the field ; then begin 

 at one edge of the specimen and with the lateral 

 movement (right to left or vice versa) make it 



pass across the field. Move the slide forward with 

 the vertical movement the amount of space which has 

 been previously determined and by a return action of 

 the lateral movement, bring it across again and thus 

 through the entire specimen, or until the object is 



found. 



Nose -Piece. This being the lower end of the 

 body, to which the objectives are attached, it is import- 

 ant in so far as it must be accurately made. As has 

 been stated, it has the society screw. Previous to 1857 

 each maker followed a standard of his own and this to 

 a great extent is still the case on the Continent. The 

 Royal Microscopical Society, of London, appreciating 

 the inconvenience of this diversity, recommended a 

 standard thread of thirty-six to the inch with an external 

 diameter of 0.8 inch, which was finally adopted in 

 England and this country. The Society supplied to 

 the makers a so-called standard hob or tap with which 

 to gauge the thread. Unhappily, however, these taps 

 have not been made to a standard, as there is a 

 variation in those which are sent out by the Society, 

 so that, while the public is under the impression that 



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