102 HOW TO SEE WITH THE MICROSCOPE. 



nineteenth band of the Nobert test-plate was said " to 

 be a matter of faith rather than of sight." The curious 

 reader is informed that the original of the quotation 

 will not be found in the last edition of the ' ' Microscope 

 and its Revelations ! " 



Again, the high-angled objective, as at present con- 

 structed, is an entirely different affair from that of 

 former times. In place of achromatism, then thought 

 to be the ultima thule of perfection, the finest glasses 

 now made can hardly be said to be achromatic. And 

 then, again, the immersion system has been adopted 

 with its manifold advantages. Improvement upon im- 

 provement has almost marked the rolling months of 

 the calendar, while each succeeding year, to the number 

 of ten or more, has been richly laden with the fruits of 

 the optician. 



In this wonderful march of progress, our own coun- 

 try, I am proud to say, has ever been at the front, and 

 with colors flying. As before stated, Spencer, with his 

 resolution of the navicula, commenced this march of 

 progress, and slackened not the pace until the reputa- 

 tion of American objectives were duly acknowledged 

 abroad. Then, indeed, he retired for a time, resting 

 gracefully on his well-won laurels; and now appears 

 Tolles at the van, who with almost superhuman genius 

 and energy grapples with the very laws of optics, and 

 bends them to his inflexible will ! 



Notwithstanding that the reputation of the country 

 was quite safe in the hands of Mr. Tolles; Spencer, 

 after a year or two of rest, again comes forward, assisted 



