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ON SMITH AND BECK’S ACHROMATIC MICROSCOPES. 275 
microscope is then described, and the principle of its con- 
struction defended against the attacks of those who are in 
favour of the old monocular form of instrument. The in- 
creased demand for binocular instruments seems to indicate 
that the old arrangement is doomed. Men of fifty, who have 
for thirty years used the monocular instrument, may repudiate 
the more recent instrument, but as long as the fact remains 
than men see better with two eyes than one so long will it 
happen that those who have once appreciated the advantages 
of a binocular microscope will not think of going back to the 
instrument which only allows the use of one eye. 
After describing first-class instruments, Mr. Beck then 
gives an account of the third- and fourth-class instruments. 
Most persons are aware of the nature of the instruments 
which, under the name of the Popular, Universal, and Edu- 
cational Microscopes, have been manufactured by Messrs. 
Smith and Beck. The work finishes by a chapter on the 
instruments and materials used in mounting objects. 
To those who are the fortunate possessors of one of Smith 
and Beck’s first-class compound achromatic instruments this 
volume will be found exceedingly useful in enabling them to 
understand the applications and capabilities of their instru- 
ment. ‘To all interested in the structure of the microscope 
this volume, giving an account of the actual work of one of 
those great houses to which Mr. Lister has succeeded in 
giving something of the reputation of his own great name, 
will be found to contain a vast amount of useful and interest- 
ing matter. 
The work is published in large octavo, and is illustrated 
with twenty-eight most beautifully executed plates. Most of 
these are devoted to the illustration of the apparatus described, 
but some of the plates are devoted to the illustration of test- 
objects. Some of these are remarkable for the faithful 
manner in which microscopic structure is depicted. We 
would especially refer to the beautiful drawing of the tarsus 
of the Tegenaria atrica, a very common form of spider, in 
which the various minute hairs covering this organ are given 
in the most complete and accurate manner. The figure, again, 
of Arachnoidiscus Japonica, a beautiful diatom first found in 
sea-weed from Japan, is quite an achievement in illustration, 
and seems to indicate the importance of giving different 
aspects of even minute objects like diatoms. There is also a 
beautiful plate of Polycistina on a dark ground, and another 
of polarized objects, all instructive in relation to the use of 
the microscope, and suggestive of the way in which micro- 
scopic objects may be represented. 
VOL. V.— NEW SER. U 
