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 have not extended further, MM. Pistor and Schick also, 

 whose great scientific accuracy is universally acknowledged, have resolved 

 to apply their care to the 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 Scbiek's new mi- 

 croscope, and a letter alluding to tliis subject is found in the same vohime of 

 Poggendorff's ^n«a/en, 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 Plosrs 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 Plosl — 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 Ehrenberg wrote this he has had 

 the opportunity of comparing Schick'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 

 theobject was, withapower of380, 10" 6'"; with a power of 800, 1'^''. 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 



2 r2 



