68 MEMORANDA. 



the scale of the Podura, and the lines and cross-bars on the 

 fan-shaped scale of the Morpho Menelaus. 



This is as far as most persons care to go. Nevertheless, I 

 do not deny, that beyond this there does exist a very limited 

 class of what I call '^excruciating objects" for which "the 

 Binocular" is not so well adapted ; and for such profoundly 

 erudite researches the determined observer may keep an old 

 single barrel, which can be adapted, in place of the double 

 one, in less than half a minute. It should be contrived to 

 pack into the same case, and should be called " the excru- 

 ciating tube." 



By its means, together with a Powell's one sixteenth or a 

 Wenham's one twenty-fifth, he may possibly be enabled to 

 solve such infinitesimally argute problems as whether the scale 

 of Pontia brassica has, or has not, diagonal as well as longi- 

 tudinal lines; and whether the dots on Pleurosigma angu- 

 latum are of a round shape, as represented in ' INIicroscopical 

 Journal,^ vol. iv, PI. XII, or hexagonal, as revealed in Dr. 

 Carpenter's 'Revelations,'* p. 307; — researches which, to 

 use the quaint words of Dr. Goring, are '' about as profitable 

 to ourselves and our fellow- creatures as if we were engaged 

 in the sublime and important occupation of determining 

 whether the small star of £ Bootes is of a greenish blue or 

 bluish green, or whether some nebula is very gradually, or 

 very suddenly, much brighter in the middle.''t — Henry U. 

 Janson, Pennsjdvania Park, Exeter. 



* It is to be rei!,Tcttcd that it sliould liave been stated iu that work that 

 tliere is a difficulty in adapting the Weuham binocular to " the varying 

 distances of the eyes of dilTcrent individuals." Tlie truth is, the said adap- 

 tation is one of the best things about it, and consists merely in drawing out 

 or pushing in the l^A'o cyc-tubes. 



f ' Microscopic Illustrations,' p. 211. 



