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THe NortHeRN Microscoptst. 


No. 21. SEPTEMBER. 1882, 



A PLEA FOR WIDE APERTURES. 
A reply to Prof. Abbe’s paper ‘‘On the Relation of Aperture and Power in 
the Microscope.” 
N the following remarks we shall consider the microscope solely 
as an aid to vision in the prosecution of research, assisting the 
observer by presenting to his eye a true but magnified image of 
some minute particle or organism, that he can behold it as in its 
natural condition, and study its character and details with facility. — 
It is well to keep this view steadily before us, as the above is the 
main purpose for which the instrument is constructed, and all 
other considerations are subordinate to it. As the revelations of 
the microscope are assuming a more important position every day, 
as observations are recorded in many journals, and as the inferences 
drawn by the student of to-day will serve to guide or misguide the 
men of to-morrow, it becomes of vital importance that the optical 
portion of the instrument shall not lend a hand in passing down to 
posterity distorted and hazy approximations of the truth. 
For the purposes of scientific work we are about to argue (within 
certain well defined limits) for wide apertures only, and would 
strongly advise the young beginner who is making any department 
of Natural History his study to purchase his objectives, of apertures 
as nearly as he can afford, to those which we shall recommend. 
Not—be it understood—that we wish to discourage any student 
who is obliged to select cheaper lenses. He will find in these a 
magazine of power sufficient to satisfy all his early requirements, 
and as the differences between lenses of fair and excellent qualities 
are matters which require a fine judgment and great practical 
knowledge for their decision, a student might very possibly per- 
ceive no difference between an objective costing eighteen shillings 
and a well corrected wide aperture lens costing fifty shillings. 
Indeed, he might think the former the better one ‘of the two, des- 
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