ON SMITH AND BECK’S ACHROMATIC MICROSCOPES. 273 
period their artificial generation is very uncertain. This little ex- 
periment is a very simple and instructive one, and may be per- 
formed by any one who will take the trouble to follow out these 
instructions,” 
But the most useful part of this volume to the advanced 
student is an appendix, in which the author gives a classifica- 
tion and scientific description of the fungi which have been 
more generally alluded to in the previous pages of the work. 
For those who have not their hands already full of work, and 
prepared to strike mto a new field, we promise them a mine 
of interest in Mr. Cooke’s pages, and a world of undiscovered 
beauties to work in. 
A Treatise on the Construction, Proper Use, and Capabilities 
of Smith, Beck, and Beck’s Achromatic Microscope. By 
Ricuarp Beck. London: Van Voorst. 
Ir is not often that the makers of scientific instruments 
are the most skilful exponents of the principles of their 
structure or the authors of discoveries made by their use. 
Nevertheless, many departments of practical science afford 
exceptions to the rule—none more so than the inventors and 
makers of improvements in the microscope, and every micro- 
scopist will recollect that Joseph Jackson Lister, after he 
had overcome the difficulties of making a compound achro- 
matic microscope, set to work to make observations there- 
with, and produced a series of highly interesting observations, 
which were published in the ‘ Philosophical Transactions,’ on 
some of the lower forms of Tunicated Mollusca. It may not 
be generally known that, so little was the microscope appre- 
ciated as an instrument of research by those who conducted 
the business of the Royal Society in 1838, that when Joseph 
Jackson Lister sent his first great paper to that society, on 
the construction of achromatic glasses, and accompanied 
it with various observations on the mechanical parts of 
the instrument, the paper was sent back to him on this 
account, with a request that, as the microscope was, after all, a 
mere toy, he would omit any reference to what he considered 
mechanical improvements. In this fact we see how danger- 
ous it might be to commit the interests of science to any 
select body of men, and that it is only in the perfect freedom 
of voluntary association that science can progress. The 
Microscopical Society was shortly after founded, one of the 
