420 
POPULAR SCIENCE REVIEW. 
easiest and simplest manner^ and proceed only by degrees to 
the more complex. While no one would dream of being able 
to perform any work requiring special skill without any 
previous thought or practice^ many seem to think that the 
highest magnifying glasses ought to be manageable even by 
those who have never been in the habit of using moderately 
high powers. 'No one should attempt to work with a 
until he can use a -iV quite readily ; and before we touch the 
tV we should be thoroughly familiar with the use of the J. 
The higher the power the more difficult are all the little 
manipulations required for arranging the specimen^ applying 
the thin glass^ focussing, &c., to say nothing of the greater 
difficulty of obtaining specimens sufficiently thin and perfectly 
flattened out, without the slightest derangement of their 
delicate texture. 
Unless, therefore, the observer proceeds on by steps, v, 
ih) will stand little chance of success. But, on the 
other hand, if the student steadily works on, and takes 
the requisite precautions in preparing the specimens, he will 
be surprised at the vast number of new facts he observes with 
the aid of very high powers; nor can it be doubted that if the 
magnifying power could be still further increased, yet more 
important points would be discovered. 
During the last quarter of a century great advance has 
been made in the manufacture of high magnifying powers, 
and within the last five years glasses have been produced 
magnifying from 1,500 to 2,500 diameters; and it has been 
clearly established, not only that the investigation of the 
structure of the most minute organisms may be greatly 
advanced by their use, but that the fundamental arrangement 
of many of the most important tissues of man and the higher 
animals cannot be demonstrated by object glasses possessing 
a less degree of magnifying power. 
The first fiftieth which was made for me by Messrs. Powell 
& Lealand was completed and shown at the Microscopical 
Society on October 12th, 1864. It magnifies nearly 3,000 
diameters with the low eye-piece. The same makers pro- 
duced a sixteenth in the year 1840 and the twenty-sixth in 
1860. 
I was not aware until a short time since that Mr. Wenham, 
to whom science is indebted for so very many important 
improvements in our instruments of observation, was really 
the first who succeeded in making a-^^y. Mr. Wenham^s glass 
was completed so long ago as June, 1856, and I have lately had 
ample opportunity for examining it carefully and studying 
different objects under it. The principle of its arrangement 
is somewhat different to that of Powell & Lealand^s object 
