MICROSCOPIC TESTS. 



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. 



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- F . ^ 



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 



