21 



NEW BOOK 



The Anatomy and Physiology of the Blow-Fly (Musca Vomitorid). — ■ 

 A Monograph. By Benjamin Thompson Lowne, M.R.C.S. 

 Eng. Illustrated with ten plates. London : Van Voorst ; 

 pp. 121. 8vo. 



We have been favoured with a sight of the proof sheets of the 

 above work, which is now nearly ready for issue to the subscribers. 

 We have not time to execute a review which shall do justice to the 

 merits of Mr. Lowne's elaborate monograph, and, in fact, we doubt 

 whether much more could be done than refer to the work itself. 

 A more comprehensive treatise on the microscopic anatomy of a 

 single insect has, probably, never been published, and we sincerely 

 hope that the author's labours will receive their due appreciation. 

 We feel bound to add that this work owes its origin to the Quekett 

 Microsco]:>ical Club, 



On the Observations necessary for Correcting Object 

 Glasses. By F. H. Wenham.* 



For this purpose, a particle of mercury is placed upon a slip of 

 black glass. A piece of watch spring, or the thin handle of a spatula, 

 is held up at its end by the fore-finger of the left hand, and slapped 

 smartly down on the mercury, which is thus beaten into powder in 

 the form of numerous minute globules. Of these, a larger size is 

 selected for correction for colour, and a minute one for ascertaining 

 the errors of figure and centering and state of the oblique pencils. 



The globule must be illuminated by direct candle or lamp-light, 

 and not by daylight, as the latter will not allow perfect correction 

 to be obtained. The light requires to be set as close as it can be, 

 and, of course, in the highest powers when there is little distance 

 in front it must be very oblique, but this is of no consequence, as 

 it is not the globule itself, but the spot of light reflected from it that 

 is required to be seen. 



The lens to be tested is adapted to the microscope having the 

 ordinary Huyghenian eyepiece. On placing the globule either in or 



* Extracted from trie Monthly Microscopical Journal. 



