J. Lawrence Smith on the Inverted Microscope. 239 
ward of two years, as it furnishes all that can be desired. The 
eye-piece micrometer ordinarily in use, consists of a glass with 
divisions drawn in it, contained in a special eye-piece adapted for 
its use ; and whenever the measurement of an object is required, 
we replace the eye-piece used by the micrometer eye-piece, and 
move the object on the stage, so that its image falls on the mark- 
ing of the micrometer. With all its advantages this form has 
inches into N, turns freely in it, and is retained bya small screw 
” passing through N and playing on a grove in G. On the upper 
. Part of G there is a small rectangular opening in a little mechani- 
cal arrangement as seen in m. ‘The various eye-pieces are so 
mounted that when placed in the tube G, the planes of their foci 
Ot OGe Secose oo iw poipetie> OG patik Mes Se eee 
past 
Scope, I am fully satisfied of the practical superiority of the latter for general 5 
ith i n be made wi and co 
ith it, observation ca: ith more ease mfort, the light ows 
“Inits of more convenient and effi ent, chemical re-agents i 
to the th the greatest facility, without endangering the instrument, and 
the slides be moved or chan with the utmost facility, 09 with perfect 
safety to the object- themselves. instrument is so firm a 
a fi ; —? v8 _ reg Pageomeni and admits of the attachment of 
very collateral appliance. I shall never willingly return to the habitual use of an 
, per ec- 
tion itself, and seems neither to absorb as distort the luminous rays in the slightest 
degree, Respectfully yours, J. L. Rippe. 
