1895 THE MICROSCOPE. 15 



QUESTIONS ANSWERED. 



Note. — Dr. S. G. Shanks, of Albany, N. Y., kindly consents to recehie all sorts of ques- 

 tions relating to microscopy , ivhethet' asked l>y />' o/essionals or amuteu> s. Persons o/ aL 

 f ades oj" experience, Jrom the beginner upiva'd, art- -a'lcunie to the bentjits ■•/ thts dep<i< ' 

 tnent. The questions are numbered Jor /uiure t eference. 



214. Can you give me the addresses of Messrs. Powell <.C' Lerdand 

 and R. &; J. Beck of London., as I desire to obtain the catalogues 

 of the above firms f 



R. & J. Beck, Manufacturing Opticians, 31 Cornh 11, London. 

 E. C, P-]ngland. Powel] & Lealand, Manufacturing 0}>ticians. 

 London, England. 



215. Of whom can I obtain the Stephenson Erecting Binocidar 

 Dissecting Microscope, described in Carpenter^s work on the Micro- 

 scope f — H. L. B. 



John Browning, Manufacturing Optician, 111 Minories, 

 London, E., England. 



216. What method will harden in the shortest time, tumors or his- 

 tological material f — /. R. 



Absolute alcohol will harden small pieces of tissue in a few 

 hours, but may produce much shrinkage or (list irtion. Try 

 FoFs solution : 



Picric acid. Saturated aqueous solution, - - - 10 parts 

 Chromic acid, 5 grains to one oz. of w.der, - - - 25 " 



Water - - - - 65 " 



Mix. 



It will harden small pieces of tissue in 24 hours. The picric 

 acid stains the tissues also, but other stains may be used if de- 

 sired. 



217. Hoiv shall I proceed to collect and examine the impurities 

 floating in the air of a work-shop ? — E. A. B. 



The floating dust, etc., work-shops and school-rooms may be 

 caught in this way. Prepare slips of glass by smearing a small 

 area with glycerine. Place these slips in different places about 

 the room during working-hours. Let tht^m remain during t le 

 night so that the floating particles may tall upou the glycerine 

 and be retained. Add more glycerine if necessar}-, c »ver, ring 

 with varnish and examine. 



