Miscellaneous. 437 



his materials, and a careful selection of examples, Dr. Griffith has 

 rendered his work at once a manual of vegetable and animal ana- 

 tomy and physiology and a guide to the general classification of 

 organized bodies ; and there is no doubt that the student who will 

 take it as a guide, and, in accordance with the author's evident in- 

 tention, work carefully through the series of easily obtained exam- 

 ples of animal and vegetable structures described in it, will find 

 himself, at the end of his course of study, already in possession of a 

 very considerable amount of information, and quite prepared to fol- 

 low out any particular line of investigation upon his own account. 

 It is, indeed, manifestly with a view to the latter point that Dr. Grif- 

 fith has prepared this Text-book, and in this he seems to us to have 

 been eminently successful : we are acquainted with no work so well 

 adapted to set the reader in the way of independent microscopic 

 research. The amount of valuable information compressed into the 

 pages of this little volume is perfectly astonishing, as is also the 

 quantity of beautiful and characteristic coloured figures which the 

 author has succeeded in bringing together in the twelve plates with 

 which the work is illustrated. 



To the practical consideration of the microscope itself Dr. Grif- 

 fith does not devote much space, and he altogether avoids the dis- 

 cussion of the comparative merits of different makers and of different 

 modes of construction, confining himself to a brief description of the 

 essential structure of the instrument and of the uses of its different 

 parts. In his concluding chapter, however, he enters upon the con- 

 sideration of the scientific principles involved in the construction of 

 the microscope, including the phenomena of refraction and reflexion, 

 the nature and effects of lenses, achromatism, and polarization of 

 light ; and we have seldom, if ever, seen these somewhat difficult 

 matters so simply and perspicuously treated. 



With regard to the preparation and mounting of microscopic 

 objects, special details are scattered throughout the work, indicating 

 the particular treatment best adapted for the successful preservation 

 of certain groups of objects — the general plans to be adopted in any 

 ease being very shortly and simply described in the second chapter. 

 Small as is the space devoted to this important subject, the methods 

 recommended (which indeed are those most commonly in use among 

 microscopists) are thoroughly well described ; and perhaps it is 

 better for the beginner to have one good set of methods laid before 

 him, than to be left to select those which may hit his fancy from a 

 collection of all the processes adopted by various microscopists. 



MISCELLANEOUS. 



Dredgings in the Freshwater Lakes of Norway. 



To the Editors of the Annals and Magazine of Natural History. 



Gentlemen, — I believe the following extract from Mr. G. O. Sars's 



account (given in the 'Nyt Magazin,' Christiania, for 1862) of his 



dredgings in some of the freshwater lakes of Norway has not ap- 



