Microscopes at the American Exhibition. By J. G. Hunt. 25 
class are not instruments of precision. It is a mistake to place in 
the hands of beginners bad tools to work with. Wherever a micro- 
scope is cheapened in cost by inferior workmanship, it is unfit for 
the student. It had better be in the hands of the expert who will 
eliminate its errors by his previous experience. Drop all me- 
chanical luxuries in order to reduce expense, but give the best 
workmanship to the beginner. Much of this class of work sent 
here from abroad is so inferior that time would be wasted in speak- 
ing of it further. 
In the construction of objectives great advances are to be 
noticed. On this subject my remarks will not be confined to lenses 
only which were on exhibition. 
The patent system of Mr. Wenham, by which corrections are 
obtained by a single flint lens, was exhibited very fully before the 
judges. From the Ith to the ^th were on trial. They gave 
evidence of undeveloped microscopical potentialities of an advanced 
order, hut their mounting and the mode of testing, justice compels 
me to say, were unsatisfactory. I therefore forbear judgment until 
I shall see more careful work. 
Mr. Crouch’s lenses were of the first grade. Those on exhibi- 
tion and those seen since, without revealing any extraordinary 
optical qualities, are exceedingly fine in field and definition for their 
cost. Their corrections for achromatism resemble strikingly the 
Wenham lenses. 
Beck’s objectives form a series with which I am familiar, and 
they retain their character for many excellent optical properties. 
Without aiming at maximum angle, they are as nearly achromatic 
as lenses can be made. Their T %th is not inferior in performance 
to any other of equal power made, and, in use, is the most satis- 
factory lens of the series. But I must say these objectives — the 
adjustable ones — are not accurately mounted. The screw-collar 
jolts around from degree to degree in a way that forbids hope for 
the finest performance. The old plan of adjustment is retained, 
viz. of traversing the front combination, which must be compara- 
tively defective. Lister’s plan of adjustment and correction did 
well enough for twenty-five years ago, but modern microscopy 
demands a higher grade of work than that. 
Fortunately, that demand is satisfied. The new -|th, so called 
by Powell and Lealand, brought into this non-achromatic world by 
what process of microscopical parturition we are not informed, ranks 
highest of all foreign objectives I have yet examined. Its correc- 
tions reveal a bluish-green light, and its definition marks an entire 
new era in English microscopy. It is difficult indeed to judge of 
this grade of lens because of our former defective experience. I 
cannot call its definition brilliant, but it is sharp and very accurate. 
On the margin of the field a good image is formed, which is gene- 
