WITH THE MICROSCOPE. I I 



brated makers. As I have had very great experience in the use of 

 the instruments of Messrs. Powell and Lealand, I feel it right to 

 state that I have always found their work most excellent. These 

 makers have done much to perfect the compound microscope, and 

 they have produced the highest and most perfect object-glasses yet 

 made. Messrs. Powell and Lealand's folding microscope occupies 

 a very small space. It is represented in pi. IV. 



17. Binocular Microscopes. The binocular is applicable to 

 almost every kind of microscopical research, but it is not necessary 

 for the student, and I do not recommend those who are beginning 

 to work at microscopical investigation generally, to provide them- 

 selves with one. The binocular should be a separate microscope 

 altogether, or it should be possible to remove the binocular tube 

 from the body of the microscope and substitute for it an ordinary 

 single tube. Excellent and cheap binocular microscopes (about 

 io/.) are made by Messrs. Crouch, Messrs. Murray and Heath, 

 Mr. Collins, pi. VI, and other makers. (See the list of makers at end 

 of the volume.) Mr. Collins' binocular, which costs only twelve 

 guineas, is represented in pi. VI. 



M. Nachet's instrument and Mr. Wenham's perfected binocular are 

 represented in pi. V, fig. 15. Mr. Wenham has succeeded in pro- 

 ducing two or three binocular arrangements. The first plan he 

 adopted will be understood by reference to pi. X, fig. 44 ; but the 

 new method last suggested by him, and now adopted by all micro- 

 scope makers in this country is shown in pi. V, fig. 1 6. 



New Binocular for the highest magnifying powers. Messrs. Powell 

 and Lealand have recently succeeded in devising a plan by which 

 a binocular arrangement can be adapted to the highest powers. 

 Mr. Wenham's binocular now in ordinary use is suitable only for the 

 examination of objects by powers magnifying less than 200 diameters. 

 This new plan is adapted only for the higher powers, and may be 

 used with the ^. 



The prisms employed are represented in pi. V, fig. 18. They are 

 placed above the object-glasses. Of the total number of rays which 

 have passed through the object-glass, the greater part are transmitted 

 through the prism B and the straight tube of the microscope, but 

 some suffer reflexion from its lower surface, and are received upon 

 the reflecting surface E of the prism C in an oblique direction as 

 shown by the dotted lines, and after emerging from the surface, enter 

 the diagonal tube of the microscope. 



The last of the two images is less intense than the first, but still 

 it is light enough to be seen very clearly. The two images thus 

 formed are exactly similar, and the two pictures appear to the 



