35 



vantages, such as the necessity of holding the base 

 when adjusting the magnifier and the danger to 

 the eye from the projecting stem. 



The Excelsior Dissecting Microscope (Fig. I'.)) 

 can be recommended when portability is a 

 desideratum and for school use in primary work, 

 the dissecting microscope designed by Prof. C. R. 

 Barnes. This meets many conditions of a dissect- 

 ing microscope in a simple manner. 



There is a variety of more complex forms, 

 giving a number of advantages, such as stability 

 convenience of varied illumination, delicate means 

 for and long range of adjustment, jointed arms 

 for moving the lens conveniently over a large 

 field, etc., to the various descriptions of which the 

 reader is referred to catalogues. 



How to use Magnifiers and Dissecting 

 Microscopes. It is generally admitted that the 

 intelligent use of a magnifier is a great aid in 

 microscopical studies and while its use is a simple 

 matter, some words of advice may be of aid in 

 obtaining better results, or lead to doing work 

 with more comfort. In all work, whether with 

 simple or compound microscopes, it is a good plan 

 to start out with the principle not to use a greater 

 magnifying power than is necessary to accomplish 

 the results in view. 



It should be made a habit at the outset to keep 

 both eyes open. 



