314 THE AMERICAN MONTHLY [Nov 



by employing a sheet of plate-glass as a retlector instead 

 of a silvered mirror, that I get. ample light, and that no 

 injurious amount of heat is reflected. 



Limelight is well adapted for photo-micrography ; but 

 it necessitates so much apparatus — gas-cylinders, regula- 

 tors, jet, water-tank, condensers, &c. — that I have almost 

 abandoned it. The acetylene light is promising, being 

 very white and actinic, if its disagreeable smell could be 

 avoided. I once remember using an acetylene bicycle- 

 lamp with considerable success. A paraffin flame has 

 scarcely sufficient intensity, except for low-power work, 

 as the exposures have to be so prolonged. On the whole, 

 I much prefer sunlight ; but of course that is only availa- 

 ble in the daytime — and in some climates a bright day can 

 never be depended upon. — English Mechanic, arid World 

 of Science. 



Extracts From English Postal Microscopical Society's 

 Note-Books. 



DR. G. H. BRYAN, F.R.S. 



Podura and Other Scales. — Although "scales of the 

 Lepisma" and "scales of Podura" find a place in most 

 cabinets, I do not remember a series of objects of this 

 class having been circulated round the P.M.S., and I ven- 

 ture to hope that the present series may afford some in- 

 struction to some of the members, and perhaps stimulate 

 them to collect a few of these interesting little objects 

 for themselves. The "Podura scale" seems to have pro- 

 duced a great sensation among microscopists about 1873, 

 when it was brought before public notice by the late Mr. 

 Beck ; but since then fresh "test objects" have supersed- 

 ed it to a large extent — viz. Pleurosigma angulatum, and 

 then Amphipleura pellucida, and these seem to have grad- 

 ually led to the improvement in lenses required for the 

 study of bacteriology. At the same time these old test 



