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ORIGINAL COMMUNICATIONS. 
Rerort of the Microscorrs exhibited at the INTERNATIONAL 
Exursition, 1862. 
In a former number, Vol. IT, n.s., p. 197, shortly after the 
close of the Exhibition, we offered a few remarks on the mi- 
croscopes contained in it; and we are now glad to have an 
opportunity of giving the able and full report upon them 
which has but just appeared in the series of “ Jurors’ Re. 
ports,” from the able pen of Mv. C. Brookes, F.R.S. 
Microscorms AND Acorssory APPARATUS. 
The recent Exhibition, like its predecessor in 1851, has been 
very complete in its display of microscopes, accessory apparatus, 
and objects. For a briet history of the development of the micro- 
scope, the reader is referred to the Report of 1851, p. 265; it may 
suffice on the present occasion to say that since 1851 considerable 
improvements have been effected both in the optical and mechani- 
cal departments of this important instrument, the employment of 
which, whether for purposes of mere recreation or of scientific re- 
search, has been so largely developed within a few years. 
As regards optical construction, a considerable accession of 
available power has been effected; some very deep powers have 
been constructed by continental artists, most of these being de- 
signed to be used with the intervention of a fluid medium between 
the external surface of the objective and the covering glass of the 
object, amongst which those of M. Hartnack are most conspi- 
cuous; but no objective yet manufactured for sale at all rivals, in 
its power of development, the =1,th of Messrs. Powell and Lea- 
land. These able artists have likewise been very successful in the 
construction of the deepest previously acknowledged powers, 
namely, those of jth and ;!;th inch focus; in these objectives 
excessive angular aperture has been judiciously sacrificed to more 
comprehensive and practical utility. 
In flatness of field, and in perfection of definition, both at the 
centre and margin of the field of view, few objectives have equalled, 
and none have surpassed, the recent constructions of Mr. Ross, 
VOL. IV.—NEW SER. G 
