THE MICROSCOPE. 85 



use the instrument as a means of research and not as a play- 

 thing. 



First and foremost, the simpler the working parts are, the 

 better. Complication means a waste of time with no corre- 

 sponding gain. When a microscope becomes a mass of 

 machinery with screws, wheels, pinions and a thousand and 

 one appliances, its sphere of usefulness is gone. 



The tube of the microscope should be short and, if the 

 owner has money for objectives, a draw tube and an ampli- 

 fier are utterly useless. The use of a draw tube is to increase 

 the length of the tube of the microscope and thus enlarge 

 the image formed by the objective, but it must be at once 

 evident that the increased size of the image is counterbal- 

 anced by a corresponding loss in distinctness and brilliancy. 

 But few objectives are made which will stand the strain of 

 the higher oculars and a draw tube. The continental workers 

 adopt the other method of using objectives of greater mag- 

 nifying power to obtain the desired amplification and it is only 

 necessary to refer to their published figures to show the 

 great superiority of their method. The writer would there- 

 fore advise instruments with short tubes, the amplification of 

 the image to depend on the objective. 



There should be two methods of regulating the distance 

 between the objective and the object : one by which it can 

 be rapidly increased or diminished, while the other works r.t 

 a greatly lower rate of speed and thus is suitable for small 

 distances. These are called respectively the coarse and fine 

 adjustments. There have been many plans for regulating the 

 coarse adjustment, but two, however, having any extensive 



