XXXIV. Notices respecting Nets Books. 



The Mia-oscopic Cabinet of select Animated Objects, with a Description 

 of the Jewel and Doublet Microscope, Test Objects, &c. .- to which 

 are subjoined Memoirs on the Verijication of Microscopic Phcenomena, 

 and an exact Method of appreciating the Quality of Microscopes and 

 Engiscopes. By C. R. Goring, M.D. Illustrated by Thirteen 

 Coloured Plates from Original Drawings and numerous Engravings 

 on Wood. By Andrew Pritchakd. 



IN preceding Numbers of the Edinburgh Journal of Science, we 

 have had occasion to speak very highly of the improvements in the 

 microscope, which have been made by Dr. Goring and Mr, Pritchard, 

 and of their joint work entitled Microscopic Illustrations, 6<.c. 



The work, of which we now propose to give a brief notice, though 

 a separate and independent publication, may yet be regarded as a 

 continuation of their former labours. The first thirteen chapters, 

 which occupy about a third of the volume, contain popular and ge- 

 neral descriptions of the aquatic larvas of insects, crustacea and ani- 

 malcula; and these descriptions are illustrated by ten beautiful and 

 highlyfinished coloured engravings. The Nth and 15th chapters treat 

 of jewelled microscopes and microscopic doublets. The 16th chapter, 

 which is one of the most important and interesting of the whole (and 

 of which we may give a separate account in a future Number), treats 

 of the history of test objects, and of the method of viewing them. The 

 objects here described are divided into two classes : 1. those which 

 serve for exhibiting the penetrating power of microscopes ; anci 

 2. those which serve to exhibit their defining power. The first of 

 these classes contain scales from the Lepisma saccharina, Morpho 

 Menelaus, Alucita Pentadactylus, &c., Lycenae, Clothes' moth, Pon- 

 tia Brassica, Podura Plumbea, and Diamond Beetle. The second 

 class contains Mouse hair, Bat's-hair, and Lycense Argus (the spotted 

 feathers). 



In chapter 17, Mr. Pritchard treats of microscopic doublets and 

 other compound magnifiers for microscopes, and of their illumination. 

 The microscopic doublet, as our readers well know, was introduced 

 by Dr. Wollaston*. Mr. Pritchard has found that in such doublets 

 the distance of the lenses which gives the best effect is equal to the 

 difference of the focal length of the two lenses, making a proper allow- 

 ance for their thickness. The proportion of the foci may be varied at 

 pleasure : " All that is requisite in this respect," says Mr. Pritchard, 

 " is, that the difference must be greater than the thickness of the 

 anterior lens, while it may be observed (in high powers), that the 

 greater the difference between their two focal lengths, the more space 

 will be left in front ; and as this is of great practical importance, they 

 should never be less tiian as one to three. I have made some very 

 good ones, differing as much as 07ie to six. Another advantage re- 

 sulting from attending to this point is, that we do not lose so much 



• It is described in the Edinburgh Journal of Srience, N.S. vol, i. p, 323, 

 also in Phil. Mag. and Annals, N.S. vol. y, p. .300. 



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