MICROSCOPIC TESTS. 
Wm 
Fig. 17. 
power would resolve this extraordinary object into an annular 
mass of stars. 
21. Seeing then that the stupendous works of creation, existing 
in regions of space at measureless dis¬ 
tances from the earth, have supplied such 
an unlimited variety of telescopic test- 
objects, it was natural to seek in other 
parts of creation where the more minute 
workmanship of nature has play for a 
corresponding series of microscopic test- 
objects. At the moment when that great 
and rapid improvement in microscopes 
was commencing, which was so powerfully 
promoted by the scientific and practical 
skill of the late Dr. Goring and Mr. 
Andrew Pritchard, it was found that 
various minute parts of the structure of certain species of insects 
could be rendered distinctly visible only by instruments possessing 
certain degrees of optical efficiency. 
Dr. Goring, accordingly, selected a certain number of these 
objects, which he arranged in a graduated series, according to the 
microscopic powers required to render distinctly visible the details 
of their structure. These objects consisted chiefly of minute 
scales, detached from the bodies and wings of certain species of 
61 
• The same object as seen with the more powerful telescope of 
Lord Rosse, is shown in fig. 18. 
It is evident from this that very little more increase of optical 
Fig. 16. 
