ee E A EEEN A VE ET re E TE EE ee 
ERECTING ARRANGEMENT FOR BINOCULAR MICROSCOPES. 31 
furnished are not good, and the use, otherwise satisfactory, of a 
good objective as an erector has not as yet afforded the advantage 
of binocular vision. The simple expedient now proposed is de- 
signed to increase the usefulness of the stereoscopic binoculars in 
ordinary use by rendering them easily available for purposes which 
require an erect image. 
Last summer I proposed, at the Indianapolis meeting of the 
American Association, to place, for certain purposes, an erecting 
objective below instead of above the regular objective of the micro- 
scope. Then, of course, the regular objective becomes the erector, 
and the accessory one below acts as the objective. This simple 
expedient, applied to Wenham’s or other non-erecting binoculars, 
leaves little to be desired for the purposes of a dissecting micro- 
scope. As a simple contrivance, the lenses of a one-and-a-half 
or two-inch objective (preferably a solid or single-combination 
one) may be packed or screwed into the upper end of an adap- 
ter which when screwed into the nose-piece of the microscope car- 
ries 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 ele- 
ant but scarcely more satisfactory arrangement is an adapter 
with sliding-tube adjustment which varies to the extent of an inch 
or more the distance between the erector and objective. Differ- 
ent powers and distances will of course be used according to the ~ 
wants of different observers. The combination which has proved 
most convenient in my hands consists of a two-inch erecting lens 
close to the binocular prism, and a two-thirds objective at a dis- 
tance, measured to its lowest end, of from three to four and a quar- 
ter inches below the erector ; giving powers of ten to fifty diameters, 
and requiring a working distance between the stage and the bi- 
nocular prism of four and one-half to five inches, which is quite 
practicable with large stands. A shorter working distance may 
be gained at a slight disadvantage. With a two-inch erector and 
four-tenths inch objective, powers of eight to fifty diameters can 
be secured without removing the binocular prism more than four 
inches from the stage ; and with a one-inch erector and two-thirds 
inch objective a power of forty diameters is obtained with the 
binocular prism three and three-fourths inches from the stage. 
When, however, sufficient working distance cannot be obtained, the 
object may sometimes be placed upon the substage, or, oftener, 
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