The Microscope. 61 



I do not undertake to say which is the best. For wood I use a 

 carpenter's vise and a very finely set carpenter's snioothing-plane. 

 Then select from the shavings for sections. Same for barks and hard 

 roots. Wm. Humphrey, Adrian, Mich. 



Boil the wood until soft, then fasten in microtome well and cut 

 with a sharp chisel. B. F. Quimby, Chicago, 111. 



7. What is the best method of sharpening the knife for 

 cutting vegetable sections ? 



A. L. Woodward. 



I use a fine hone, finishing on a razor strap, holding the knife 

 close to hone so that the back touches. The knife needs sharpening 

 oftener when used for vegetable sections than when cutting animal 

 tissues, because of the presence in vegetables of a great abundance of 

 crystals. 



Wm. Humphrey, Adrian, Mich. 



8. What is the best cement for sealing preparations that 

 are to be used with homogeneous immersion objectives? 



I use nothing but the white zinc cement, furnished by Mr. 

 Walmsley, of Philadelphia. 



J. Edwards Smith, M. D., Cleveland, O. 



Depends entirely upon the fluid to be used. If oil, such as cedar 

 oil — shellac is good. If the glycerine fluids, almost any cement an- 

 swers well. A thin solution of gelatin is good with oils, for alcohol 

 or chloroform can be used to clean off with. 



A. Y. Moore, Cleveland, O. 



10. What is the best method of adjusting an adjustable 

 objective to produce the most satisfactory image? Has the 

 plan of Zeiss (the plan is at least stated by him) any objection- 

 able features? As I understand his plan it is to mark various 

 thicknesses of covers on his adjustable objectives, then the 

 thickness of a cover being known, the best adjustment is ob- 

 tained simply by turning the adjusting collar till its index is 

 opposite the number indicating or corresponding to the thick- 

 ness of the given cover-glass. 



There is no royal road to the adjustment of objectives ; the art can 

 only be acquired by patient practice. The above-named method of 

 Zeiss— as also tbe plan proposed by A. Ross — in fact, any mechanical 

 method, all are faulty and unsatisfactory in practice. Examples given: 

 Suppose we have in hand a balsam diatom slide, having j^o-inch cover; 

 then those diatoms in contact with the under side of cover will require 



