1896 THE MICROSCOPE. 143 



quent mistake. To avoid it clean the eye piece b}' breath- 

 ing- upon it and wiping- off g-ently with a soft clean hand- 

 kerchief. 



Mounting Polycystina. — These shells may be mounted 

 as transparent objects in balsam. In the latter medium 

 thev do not show to best ad\antag-e : neither are they per- 

 fect when mounted dry without preparation as they pre- 

 sent too glassy an appearance. For perfect results heat 

 them on platinum foil, mica or some other support by 

 means of a blow-pipe flame or over a lamp. This heating- 

 will destroy the g-lassy appearance and render them opales- 

 cent. Then mount them as opaque objects and a beau- 

 tiful slide will result. 



SCIENCE-GOSSIP. 



Baltimore Inspects its Bakeries. — The Board of Heath 

 of Baltimore has appointed an inspector of bakeries, whose 

 duty will be to make periodical visits to such places, and 

 inspect material, utensils, and everything- pertaining- to 

 the operation of baking-. The aim of the department is a 

 worthy one, and conducted upon lines sufficiently wide, 

 should correct the typical unsanitar}- surrounding-s of such 

 places, and insure cleanliness among- those upon whom 

 the care or carelessness of whose persons and their sur- 

 rounding-s depends, in a g-reat measure, the public health, 

 — Americafi Medico-Surgical Bulletin. 



Flash-light Paper. — Flash-lig-ht paper, adangerless con- 

 venience for photographic purposes, is prepared (Papier 

 Zeitung-.) by coating- one side of two sheets of calendered 

 paper with starch or flour paste, then sprinkling- upon the 

 paste powdered mag-nesium, and pressing- tog-ether, to 

 cause them to adhere. After drying-, a sheet similarly 

 covered with powdered potassium chlorate is pasted upon 

 each side, so that the powdered mag-nesium contained be- 

 tween the first sheets has a layer of potassium chlorate on 

 each side. A further sheet pasted on serves as a cover- 

 ing-, and the whole, w^hich forms a thick sheet, can be cut 

 into strips. 



