1893.] THE MICROSCOPE. 77 



QUESTIONS ANSWERED. 



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

 tions relating to microscopy , whether asked by professionals or amateurs. Persons of all 

 grades of experience, from the beginner upward, are welcome to the benefits of this depart- 

 ment. The questions are number ed for future reference. 



149. How is collar correction managed? What are the ap- 

 pearances which call for opening and what for closing the 

 systems? How can I arrive at the best correction and know 

 that I have obtained it? If there is no certain and short cut 

 to proper correction, it would be a satisfaction to k?zow th 

 fact. — Dan. 



See article by Dr. S. G. Shanks in June number of A. M. 

 Microscopical Journal, 1893. 



130. Is methylated spirits the same as alcohol? — S. 



Methylated spirits is common or ethyl alcohol with 1-9 its bulk 

 of methyl alcohol (wood alcohol). The latter alcohol has a dis- 

 agreeable, smoky taste and is unsuitable for beverages, therefore 

 is duty free in England. Methylated spirits is also duty free and 

 is intended for use in the arts. 



757. What substitute may be used for the slide of the plate- 

 holder in photomicrography with high pozvers? After care- 

 ful focusing the withdrawal of the slide disturbs the focus. 

 — W. N. S. 



If the camera is steady and firm and the plate-holder fits as it 

 should do, a careful withdrawal of the slide should not disturb 

 the adjustments. Perhaps the objective is at fault ; visual and 

 chemical rays do not always come to the same focal point. 



IS 2. Will tobacco smoke injure microscopic specimens? 

 Will tobacco smoke change the color of white paper ? — R. 



Tobacco smoke, like any other kind of smoke, is finely divided 

 carbon or soot, and will injure any delicate objects, if in sufficient 

 quantity. There are other volatile principles in tobacco, but not 

 in sufficient quantities to produce any special effects. 



ijj. Is the duty on imported ??iicroscopes 40 per cent.; and 

 does this mea7i for everything in an outfit, including objec- 

 tives, eyepieces, etc., or is the latter subject to separate 

 duty? Can the duty be determined by adding the price of 

 stand, objectives, eyepieces, etc.? — A. D. P. Weaver. 



Yes, you must pay 40% on the price at which all such manu- 

 factured objects are billed to you. Not even an eyepiece can be 

 sent in to you free of duty. 



