306 Transactions of the [cums Dee a aero 
valuable record of this interesting observation, though imperfectly 
represented in the 1869 Plate. 
I wish to place upon record my belief— 
(1.) That further advance will now be made in the powers of 
the microscope by improving the lower powers, rather than by the 
construction of deeper objectives. 
(2.) That the microscope will be further improved by using a 
greater variety of glass, of various refracting and dispersive powers, 
than hitherto employed. 
(3.) By selecting differently dispersive fluids for immersion 
enses. 
I take occasion to copy from my note-book some results 
obtained by the camera lucida, and also confirmed by the Krato- 
meter,” as regards the amplifying powers obtained with the Apla- 
natic Searcher. 
OxgEcTIVE “OnE IncH.” 
Inches. Searcher. Power. 
Eye-piece B of focal length .. 2 Bra ae BE Sah 450 
oe Oe gs i Da 
+ Cc i 99 -. — .. without searcher .. 100 
OxpsecTIVE “ Har Inca.” 
Searcher. Power. 
Hye-piece B ..° 2. a0 ‘on pe mip nue i 700+ 
5, One Seelge oe! peace Tet 5 wart, Ceeely 
1) Bas fe us| Ge rithoutmearcher weet Aa ae 260 
OBJECTIVE “ ONE QuARTER” Ross (1851). 
Searcher. Power. 
Hye=piece Be awl pes. ise, a8 iby as). Vapeecle aR 
- C .. .. «a oa* Without searcher .. .. (about) 400 
OxsecTIvE “OnE Eicuru.” (5 inches of draw-tube.) 
Searcher. Power. 
Eye-pieceB .. .. «2 «« 1 eg «ee Bright 2300 
Bee without searcher a 1200 
“i C eye-piece without searcher 10 inches from object 650 
OBJECTIVE 5). 
Searcher. Power. 
Eye-pieceB.. .. .. 1 «» «. o« 4600 (estimated) 
OR without searcher a toe Se 
” 
I have generally found for the very deepest objectives a very 
low-power eye-piece of 3 inches focus, and a low-power searcher of 
1-inch focus, placed midway between the eye-piece and objective, 
productive of the most brilliant results. Having fitted up a great 
* To be described in next Number. + Fine definition. 
