T>() SELECTION AND tTgJJ 



testimony in a letter addressed to the English Mechanic. To 

 Mr. Wenliam, himself, however, is due the honor of having 

 devised a form of the binocular which is at once efficient 

 and of moderate price. Mr. Wenham's form has been adopted 

 by all the American and English makers that manufacture bi- 

 noculars, and he has. therefore, laid all microscopists under 

 deep obligations, not only by devising such simple and efficient 

 means of accomplishing a most desirable result, but by giving 

 the use of his invention freely to the world. 



Of the value of the binocular, there is a wide difference of 

 opinion, some regarding it as a mere toy, altogether beneath 

 notice as an instrument of scientific research, while others con- 

 sider it a most important addition to our means of investiga- 

 tion. Since, however, it will almost always be found that those 

 who place a high value on the binocular are those who have 

 used it most, while those who decry it know absolutely nothing 

 of its merits, and in some cases are even ignorant of the man- 

 ner of using it, the reader will have but little difficulty in de- 

 ciding on which side the truth lies. In England, where cheap 

 and good binoculars are common, this form of instrument has 

 become a great favorite with all the noted microscopists, and 

 we refer not merely to men who own microscopes as a means of 

 amusement, but to those, who, like Carpenter and others, have 

 enlarged the boundaries of knowledge by their researches. At 

 present the binocular is gaining rapidly in favor in this country, 

 and very excellent instruments are now turned out by several 

 of our American microscope makers. 



There are, of course, certain limits to the range of usefulness 

 of the binocular microscope. As at present constructed, it is 

 most efficient in the use of the low powers, and hence, there 

 are certain classes of work to which it is peculiarly applicable, 

 while in other branches, particularly certain departments of 

 histology, it is of comparatively slight advantage. And it will 

 in general be found that the principal opposition to the binoc- 

 ular has come from continental histologists, who, because they 

 found it of little use to themselves, concluded that it could not 

 possibly be of use to any one else. 



The advantages presented by binocular instruments are two- 

 fold ; the relief to the observer arising from the ability to use 



