26 ON HIGH POWERS, AND A STEADY MICROSCOPE. 
answer to this let me observe that my instrument, made by 
Messrs. Powell and Lealand, in 1860, has been in constant 
use ever since, few instruments more so; it remains steady 
at any obliquity without a clamping screw, and it bears well 
the following test :—With a th objective and an eye-piece 
magnifying t together 9000 linear, it remains perfectly steady, 
enabling you to focus almost exactly with the coarse adjust- 
ment; in using the fine adjustment there is no tremor, nor 
is there in using the transverse motions of the stage, or the 
circular motion of the stage; the object remains steady even 
with this severe trial. When so much is said in this paper 
in favour of a certain instrument, I do think it is but fair to 
set forth a fact like the above. 
Since writing the above, Messrs. Powell and Lealand have 
completed an object-glass of 3th of an inch focus. They ex- 
hibited it on the evening of the October meeting of the London 
Microscopical Society, ‘at King’s College. The object shown 
was a Podura scale, power 4000 linear, perfectly free from 
chromatic and spherical aberration, the definition and pene- 
tration excellent. The glass was made for Dr. Beale, who, 
no doubt, will make still further discoveries with so excellent 
an objective. It was thought a wonder when our friends 
produced a =1;th, still greater when their ~,th made its ap- 
pearance; but now they have reached -a th, the greatest 
wonder of all. Will not microscopists encourage a firm so 
untiring in their endeavours to improve the microscope, the 
object-glasses, and all apparatus that may in any way assist 
in developing structure ? 
