Monthly Mi ical , / , 
Senthis eeeonie and their Merits. 281 
so that they will give their greatest results requires delicate labour 
and considerable time. In this respect they are excelled by the 
higher as well as the lower powers of English and German.” 
“The ease of treatment of Hartnack’s and Schieck’s highest ob- 
jectives is certainly far less troublesome.” If this means anything 
it must refer to the delicacy of the adjustment for covering glass. 
Undoubtedly Schieck’s are far less troublesome. It is thought to 
be well known to microscopists that the delicacy of this adjustment— 
consequently in one sense the difficulty of use—is increased just in 
proportion to the approach to perfection of the lenses. Certain it 
is that Hartnack when delivering an objective made for a member 
of the Boston Society of Natural History two years ago, called the 
purchaser’s attention especially to the fact that when an object was 
best shown, the movement of the adjusting ring one hundredth 
of an inch either way destroyed the effect, as an evidence of the 
perfection of his work. As to English objectives. Dr. Pigott, in 
a recently-published article on high-power objectives, speaks of a 
certain effect being entirely destroyed by a change of this adjust- 
ment which moved the lens only z¢soth of an inch. So much for 
English lens and Hartnack’s. Microscopists know that Dr. Hagen 
is in an error as to good objectives, but correct if his remarks are 
applied to poor ones; and it is not surprising that he was “ utterly 
astonished to see how much more the hand of the artist himself 
will develop with the instrument.” 
The majority of the microscopists here are “ dilettanti or workers 
on diatoms;” this must be news to Professors Holmes, Bacon, 
Ellis, and Gray, and to their hundreds of past and present students ; 
the “truth will be respected” if it is said that there are hardly 
enough diatomists in the whole country to encourage each other. 
Dr. Hagen thinks that his attempt at “even pronouncing a 
judgment on the local instruments caused a storm of indignation 
against me by the resident microscopists,’ and accounts for it by 
the assertion that “we know that most of them are members of the 
Boston Optical Association.” Dr. Hagen here refers to the recep- 
tion of his verbal communication to the Boston Society of Natural 
History in November last. Of all the persons then present but 
two were members of that Association, and whatever indignation was 
manifested was at his preposterous comparisons of cost. Dr. Hagen 
then asserted that the American instruments cost 600 per cent. 
more than German of equal merit, and that “ English objectives of 
the most celebrated makers could be imported to advantage.” In his 
paper in the ‘Archiv’ Dr. Hagen reduces the comparative cost of 
German and French objectives to “ one-third or one-fourth as much,” 
but repeats his comparison as to the English “according to Frey’s 
statement.” Now before this paper was written the cost of import- 
ing English objectives was read in detail to Dr. Hagen, and it was 
