332 



Synonyms are given in all cases, and the distribution of the 

 species, both in the British Isles and elsewhere, is carefully 

 treated. There is, in addition, a most useful bibliography. 



The study of the woodlice has been curiously neglected, and 

 it is to be hoped that the publication of this admirable little 

 volume may be the means of inducing students of natural science 

 to devote more time to these interesting creatures. F. P. S. 



High-Power Microscopy. A paper by John W. Gordon, read 

 before the Royal Institute of Great Britain, February 17th, 

 1905. 



This short paper is very deserving of perusal by all interested 

 in general microscopy, and is, happily, so far devoid of technicalities 

 as to be intelligible to the average reader. The salient feature of 

 the paper is the description of a method, which seems to be 

 original, of producing an image of enormous amplification by 

 an improved arrangement of the by -no-means-new expedient of 

 substituting a compound microscope for the ordinary eye-piece. 

 The innovation consists of placing, in the focal plane of the 

 lower microscope, a disc of finely ground glass, the image 

 formed upon it being further amplified by the upper combination. 

 By this means the difficulty due to the relationship between the 

 angle of the beam of light and the magnification, as expressed in 

 the Lagrange-Heluuholtz theory, is removed, the image upon the 

 ground glass becoming, as it were, a definite object, free from 

 all optical restrictions, and capable of being further enlarged by 

 the superimposed microscope. It is obvious that the grain of 

 the glass, being in the focus of the upper microscope, would be 

 magnified to the same extent as the image, and would thus be a 

 fatal objection to the method. The author has surmounted this 

 difficulty by imparting to the screen an ingeniously devised erratic 

 motion, which renders the grain invisible. 



Exactly what good purpose is served by the forcing of 

 enormous amplification is quite another matter, and one with 

 which the author does not deal ; and, in the face of the very 

 considerable variance of opinion amongst the most advanced 

 opticians on this point, it would be very unwise to regard the 

 views of any one authority as ex cathedra. F. P. S. 



Journ. Quekei Micro Club, Ser. 2, Vol. IX., No. 58. April l?0i5. 



