i 
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A 
AND THE ULTIMATE POWER OF THE MICROSCOPE. 581 
the highest power, should raise in them a stronger interest for diffusing 
as much as possible the use of their instruments than it actually does; 
and then it is little to be feared that their own satisfaction, honour, 
profit, and advantage would be taken from them. I have observed the 
greatest power, although with some inconvenience, in one of Plosl’s 
best microscopes which our Academy of Sciences possesses. A better 
still, one of Amici’s best microscopes, Berlin is wholly destitute of, or it 
is not known to me, although it is very desirable that the examination 
of such an one were not inaccessible to the scientific persons of this 
town. 
It is exceedingly gratifying, that in addition to the recent very careful 
and successful exertions of M. Ober-Bergrath Schaffrinsky, which un- 
fortunately haye not extended further, MM. Pistor and Schiek also, 
whose great scientific accuracy is universally acknowledged, have resolved 
to apply their care tothe microscope; and those already produced are, as 
I have convinced myself, so excellent, that they are little inferior in 
power to my Chevalier’s, and in convenience are evidently superior.* I 
will here remark that in the microscope, clearness in small magnifying 
powers, however great it may be, is no superiority, but a property indis- 
pensably requisite to the character of a good one; and that the term 
superiority can only be applied to the greatest distinctness and conve- 
nience along with the highest powers. 
* M. Ehrenberg, it appears, was then not acquainted with Schiek’s new mi- 
croscope, and a letter alluding to this subject is found in the same volume of 
Poggendorft's Annalen, p. 188, where he says, “ The sharpness and magnifying 
power which M. Schiek has succeeded in giving to this convenient and elegant 
instrument, filled me with true inspiration ; and since its properties are founded 
on a rule determined by him for the combination of the object lenses, and several 
instruments finished at the same time gave the same clearness of image, I think 
it my duty, and advantageous to science, to make known the results of a com- 
parison of it with the best instruments in this town.” He then enumerates the 
good and bad qualities of Chevalier’s and Plésl’s microscopes, and says, ‘‘ The 
microscope of Schiek unites the chief merits of those microscopes; large field, 
extremely sharp and clear light, which leaves nothing to wish for, even in the 
highest powers ; magnifying power equal to the highest of Plésl—twice as high 
as that of Chevalier, and moreover a much greater focal distance. Besides this, 
it possesses a most convenient and elegant form, without being weak in its 
framework.” In another place: “ The great clearness of the image, and the 
due strength of light, is an advance ; but the union of all these good properties 
in such a degree is a still greater one.” Since Ehrenherg wrote this he has had 
_ the opportunity of comparing Schiek’s instrument with those of Dollond and 
Amici. His opinion was that it surpassed them in conveniency and elegance, and 
_ quite equalled them in power, largeness of the field, and focal distance. 
M. Ehrenberg adds that his measurements were made in the same plane with 
the object, and not at a distance of five, eight, or twelve inches of the eye from it ; 
and informs whoever wishes to make a comparison, that his eye-distance from 
_ the object was, with a power of 380, 106’; with a power of 800, 1'5". He 
also suggests that in comparing the power of microscopes, the mean length of view 
_ of ordinary sight should be taken as a point of measurement at 8"; and states that 
his magnitudes refer to absolute measure, and require no reduction.—W. F. 
QrQ 
