158 ON THE CHOICE OF A MICROSCOPE. 
object-glass, can be applied to most microscopes of tolerable 
size; but the wide range of rectangular stage motion, the 
circular rack movement, and, in Mr. Ross’s instrument, the 
clamping arc, belong to the largest microscope only, and can- 
not be applied to any other. I repeat, then, again, with great 
feeling, the advice already proffered to those about to possess 
themselves of a superior instrument: Be satisfied with nothing 
short of No. 1; for that microscope alone includes or has 
power to include all the eight above-mentioned advantages. 
The convenient mechanical contrivances, moreover, of the 
double nose-piece, the sub-stage, and the double arm to the 
plano-concave mirror, are managed with far greater ease and 
efficiency when attached to the largest microscope, because of 
its great solidity and steadiness ; and I am here reminded to 
speak of the pleasant sense of security with which this 
steadiness of a first-class microscope stand inspires you; the 
complete control thereby afforded over the adjustments and 
various apparatus connected with the instrument, without a 
chance of disturbing it from its given position, must be 
realised to be properly appreciated. 
And as to the loss in such a microscope of that portability 
which is so much prized by many, this is a want which can 
easily be supplied by one of those small stands of trifling 
cost. (about which I shall have to speak again presently), 
with such limited apparatus as is required for travelling and 
seaside excursions, reserving the large instrument exclusively 
for home use. 
I was seduced myself for many a year into the error of 
sacrificing the great advantages of steadiness and mechanical 
contrivance to the charms of portability and the possession 
of a complete set of object-glasses; but I now at length see 
how great was my mistake. If, then, any of my readers 
require a portable microscope, and will kindly receive a 
lesson from my failures, I would say to them, Have it by all 
means, but dJesides, not instead of, a large one. And as to 
your object-glasses, I would say, most decidedly, if you cannot 
afford to have everything, sacrifice even these in a measure 
to your microscope stand. Better secure the very best 
stand that can be got, with a couple of good useful object- 
glasses, than a second best with a dozen, patiently waiting 
to increase your stock of these as your means will allow you. 
It is wonderful what can now be done, with such an instru- 
ment and apparatus as I am advocating, with large aperture 
l-inch and +-inch object-glasses of modern construction !* 
* The cost of this instrument, by Mr. Ross, called in his catalogue No. 1a, 
with bull’s eye condenser, achromatic condenser, parabolic reflector, double 
s 
