THIRD CLASS MICROSCOPES. 



37 



demonstrations, dissecting, and many other purposes a 

 small microscope is exceedingly useful. 



Another cheap instrument, which is furnished by several 

 makers, is shown in Fig. 23 ; it has a sliding body for 

 coarse adjustment, a fine 

 adjustment, draw - tube, 

 wheel of diaphragms, tube 

 fitting for substage appa- 

 ratus, plane and concave 

 mirrors, one eye-piece, i- 

 inch and J-inch objectives, 

 and stand condenser, in 

 mahogany case, for which 

 is charged the moderate 

 price of 5/. 12s. 6d., to 

 which can be added after- 

 wards a polariscope for 

 25^., a camera lucida 6s., 

 and a stage micrometer 

 for 5^-. 6d. 



Equipped with one of 

 these instruments, which 

 are remarkably steady, 

 being hung on the Jack- 

 son model, the student 

 is ready for an immense amount of work, and it is 

 certainly much better to invest in an instrument such as 

 this than to waste money on a cheaper instrument which 

 has not the Society's screw. In the purchase of a low- 

 price stand, we would give the student the following 

 advice : Never purchase a cheap instrument made upon 

 the Ross model ; never purchase one which will not take 

 objectives with the Society's thread without an adapter ; 

 never purchase an instrument without a fine adjustment, 



FIG. 23. 



