156 THE MICEOSCOPE. [July, 



scarcely, if at all, inferior to that of the geared movement. An 

 ordinary slide in position is shown at d. This stage was made 

 October, 1S90, to my order and from my drawings, by the Mc- 

 intosh Optical Company of Chicago, from whom I learn that it 

 is now furnished with many of their own instruments, being 

 adapted to the round stage-plate of their microscopes by placing 

 under it a thin false stage-plate which bears beneath a socket that 

 slips into the central opening of the stage. 



EDITORS 



"^DEPARTMENT 



QUERIES AND ANSWERS. 



Questions o^ all sorts relating to microscopy will be received by the publisher and re/erred 

 to Dr. S. G. Shanks, of Albany, N. Y.,7vhose replies luiil begivenin this di'partment. Each 

 question is numbered Jor future reference. 



48. I have some ziJic ceinetit which does 77.ot harden properly 

 nor becojne 'white. What is the remedy? 



Zinc cement should be thoroughly stirred and tempered with 

 good benzol or turpentine before using. If this does not help it, 

 throw it away and procure a good article. 



49. Why is it that balsam 7nounts kept in clips for a week 

 or more will not hardeii until the superjiuous 7nedium is 

 clea7icd away, theti the air r?i7zs in and spoils the 77ion7it? 



Balsam must necessarily shrink \vhen the solvent evaporates. 

 This must be provided for and time given for the medium to 

 harden. If air runs under, gentlv heat the mount until the soft- 

 ened medium flows to the edge, and supply a drop or two of fresh 

 medium to allow for shrinkage. 



50. What is the 7nethod for 77iou7iti7ig dendritic spots on 

 paper? 



Mounted dry, in a shallow cell, will present the most natural ajD- 

 pearance. 



51. How may cocoliths a7id other orga7iis77is fro7)i chalk be 

 7?to?(7ited? 



These are best mounted in balsam ; some of them are very 

 pretty as dry (opaque) mounts. 



52. Is it C077177107Z for vorticellcc to be attached to cy clops? 

 Certain branched vorticellai are common on cyclops, also on 



many aquatic larvae of insects. 



