18 THE MICROSCOPICAL NEWS. 
” ae E uw 1 u 
If now we select a 4”, a 2”, 1”, “3, “4, “3, and ",; from two 
catalogues, one Messrs. Powell and Lealands’, the other from a 
catalogue having a third series, we shall find their prices as follow : 
Fourtines ots 1'@) $.' £1 ro "ae O° 2 er sore 
Wwo-inen.... TA. “2 15 Me 12° 2) Verna ae 
Gnemen-. 30°...) 3/73 ie Lor © 17,0 
Halfinch’... 40° ... °4 4) OWS... Aerie ere ee 
Quarter *./. 95° .2.. 5. SOUR. V7er a ee 
@One-<ighth Tod? .. . 7 7) Fem cree: 2 50° 16 
One-twelfth 145°... 12°22" ‘oF. 266" 4007 8 
#301416 70 £12 56 6 
So it will be seen that while “a good set” of English objectives 
may be had for £10 to £12, yet a set of good English objectives 
costs over £36. We should like to see these fzwo series exhibited 
side by side, when in the words of the A. M. M. J., so neatly repro- 
duced by the member of the Manchester Microscopical Society, 
there is no doubt that “the difference between them” would 
be ‘‘so striking as to attract universal attention.” If any one 
still believes in the excellence of a cheap 2” of 12°, let them 
exercise their ingenuity on the Podura scale until they have re- 
solved it. 
A few more words and we must conclude. Dr. Carpenter has 
advanced such a powerful argument in support of the aperture 
shutter that we cannot overlook it. He stated having made a trial 
of two half-inch objectives of 90° for the study of Polycistina, the 
perspective was exaggerated and so he cut the aperture down with 
a stop to 60°, and finally to 40°, ‘‘ when the perspective was true.” 
The results of this cutting down of the aperture were so encourag- 
ing that he ordered one specially to be made for him of 40°, and 
no doubt this was necessitated by the exceedingly short working 
distance of a half-inch of go’, already pointed out by the Editor on 
page 104 of “Practical Microscopy.” Why not have used the 
aperture shutter, or, as we would have preferred, have used a 
one-inch of 40°, when the observer would have had double the 
amount of penetration that he had with the half-inch. 
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