2 
The present catalogue includes, in addition to this new series, most of our 
older achromatic objectives and ordinary eye-pieces. For although there is every 
reason to assume that in the course of time the apochromatic lenses, at least in 
the more difficult departments of microscopical research, will entirely supplant 
the older objectives, yet there are a great many problems in microscopy that do 
not demand the highest attainable degree of perfection for their solution and in 
the plurality of such cases the former achromatic microscope will be all that is 
needful, provided it is good of its kind and judiciously and carefully made. 
The objectives and eye-pieces of the older type have certainly this advantage that, 
thanks to their much simpler construction, really good lenses of this class can 
be supplied at considerably lower prices than the lenses of the new series which 
are much more complicated and involve in their production an extraordinary 
degree of manual skill. 
For these considerations we have, in publishing the last edition of our cata- 
logue, omitted from the list of our foi-mer objectives only those numbers whose 
special purpose is at present undoubtedly better realised by the apochromatics 
— namely a few of the low power dry lenses of relatively large aperture and 
the very short and very long focus lenses in the series of water and homogeneous 
immersions. 
The original achromatic objectives, moreover, li a ^' e been 
considerably improved in detail by the use of the new varieties 
of glass and such other alterations as their type of construction 
permitted. The higher powers of these lenses — both of the dry and immersion 
series — where the advance thus effected is relatively considerable, might be 
termed, after the example of other makers, "s emi - ap o ch r o m at i c lenses". 
The original prices of these systems have not sustained any change l)y 
these improvements. 
In the special catalogue of 1880 we made a l)eginning and introduced 
a rational system of designation of the objectives and eye -pieces of 
the new series in contradistinction to the prevailing purposeless and arbitrary 
method. 
Although we consider this system to be more practical than any of the 
usual conventions of lettering and numbering, and though its universal adoption 
would constitute a decided step in advance, we consider it nevertheless wiser 
to desist, for the present, from redesignating our older (achromatic) objectives. 
