12 A New Erecting Arrangement. 



the upper end of an adapter which, when screwed into the nose- 

 piece of the microscope, carries them up close to the binocular 

 prism, and into the lower end of which, lengthened more or less 

 by two or three adapters of various lengths, the object-glass may 

 be screwed. A more elegant but scarcely more satisfactory arrange- 

 ment is an adapter with a sliding-tube adjustment, which varies to 

 the extent of an inch or more the distance between the erector and 

 objective. Different powers and distances will, of course, be used, 

 according to the wants of diflferent observers. The combination 

 which has proved most convenient in my hands consists of a 2-inch 

 erecting lens close to the binocular prism and a |--inch objective at 

 a distance, measured to its lower end, of from 3 to 4^ inches below 

 the erector; giving powers of 10 to 50 diameters, and requiring a 

 working distance between the stage and the binocular prism of 4^ 

 to 5 inches, which is quite practicable with large stands. A shorter 

 working distance may be gained at a shght disadvantage. With a 

 2-inch erector and a xVinch objective, powers of 8 to 50 diameters 

 can be secured without raising the binocular prism more than 

 4 inches above the stage ; and with a 1-inch erector and f -inch 

 objective a power of 40 diameters is obtained with the prism 

 3| inches from the stage. When, however, sufficient working 

 distance cannot be obtained, the object may sometimes be placed 

 upon the sub-stage, or oftener the sub-stage removed and the body 

 racked down, so as to focus through the empty stage upon the table, 

 a block or box, or an extemporized stage occupying the usual posi- 

 tion of the mirror and illuminated by the mirror after the method 

 suggested by Mr. James Smith. In this case it is often desirable 

 to increase the working distance between the prism and the object 

 by varying the lenses employed. Thus a l-|-inch objective at from 

 3f to 5f inches from the erector will give powers of 6 to 50 dia- 

 meters, and working distance from prism of 7 to 10 inches. The 

 erector may also be removed an inch or more from the prism. 

 When this latter arrangement is to be used exclusively, the appa- 

 ratus is further simplified by screwing a 2-inch objective into the 

 nose-piece in its usual position, as an erector, and screwing or slid- 

 ing over it an adapter carrying a 1^ or 2 inch objective from 4 to 

 6 inches lower down. Some contrivance is required to illuminate 

 transparent objects under the lower powers ; but opaque and trans- 

 lucent objects on a black ground can be dissected and manipulated 

 with great facility. 



The same erecting arrangement can be used in connection with 

 monocular microscopes that have no draw-tube. It may also be 

 used as a means of working Wenham's and other binoculars with 

 high powers. With powers of 500 or 1000 diameters, however, it is 

 stiU difficult to obtain good definition or to fully light both fields. 

 Teoy, New York, U.S.A., Nov. 6, 1871. 



