278 American Microscopes [sical Norra 
among opticians, but in every case their progress has been arrested 
by one insurmountable obstacle.” |What one?] “Since the recent 
improvement in correcting objectives for the thickness of covering 
glasses, comparatively little has been done.” Why he should have 
restricted the “great competition” to the last ten years, and called 
the improvements in objectives “recent,” when the competition in 
London has been active for forty years, and the ‘‘ improvement” 
was made by Ross nearly or quite thirty years ago, can only be 
explained by supposing what has been generally believed to be the 
fact, that the “improvement” and the competition had not reached 
Germany until the last ten years. So far from little having been 
done since the “improvement,” so much has been done in England 
that the Royal Microscopical Society of London, which procured 
objectives of the “three” leading London artists in about the year 
1845, in 1867-8 abandoned the whole of them as behind the times, 
and obtained new ones of the same makers. 
Dr. Hagen then makes some very just observations on “ the 
difference in the aberration of the eyes of the observers. There is 
no doubt that different observers obtain different results with the 
same instrument.” This is an important fact and an important 
admission from Dr. Hagen. It is well known to many micro- 
scopists, but is generally ignored. It is a pity that it did not occur 
to Dr. Hagen to remember what he had written in March, when he 
in October recorded some of his own observations. 
The paper in the ‘Archiv’ begins by saying that for the past 
twenty years the “ prominent excellence of American microscopes has 
been frequently mentioned” and it has been “asserted that their 
achievements have essentially excelled those of European make.” 
“To my knowledge a direct proof of this has never been exhibited, 
it has not been shown that anything has been ever better seen than 
with European instruments.” “Thus the American instrument 
constituted until recently a myth towards which all interested in 
this branch of science gazed with anxious curiosity, and prompted 
me during my two years’ residence in this country to become 
thoroughly acquainted with it, and I have spared no pains to study 
them carefully.” Here we have distinctly the task set forth, and 
the claim that he spared no pains to accomplish it. Let us see 
what were the “pains” taken. “'The members of the Microscopical 
Section of the Boston Society of Natural History, especially Mr. 
Bicknell of Salem, Mr. Greenleaf of Boston, Professors Agassiz 
and Gibbs, Mr. Edwards of New York, and Mr. Tolles himself, 
have kindly seconded my efforts.” Four of these gentlemen cer- 
tainly were competent to assist. The writer cannot say what 
Mr. Edwards or Professors Agassiz and Gibbs did for assistance ; 
but he states positively that neither Mr. Greenleaf nor Tolles “as- 
sisted ;” that Mr. Bicknell was the only one of the three who had 
