62 The Microscope. 



a different adjustment of objective from those in contact with the top 

 surface of slide. Furthermore, owing to varying conditions of the 

 eye, an expert manipulator working this slide at different dates would 

 fail to use the same adjustment of the objective. 



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



11. What is the best method for breaking down Barbadoes 

 earth before boiling ? 



G. 



A saturated solution of citric acid which acts on the iron more 

 promptly than the mineral acids. 



F. S. Newcomer, M. D., Indianapolis, Ind. 



12. What is the best size for holding diatoms in arranged 

 slides? 



Febiger's size, as follows : Acetic acid, 12 drachms ; photogra- 

 pher's gelatin, 2 drachms; alcohol, 1 drachm. 



Use a porcelain dish ; add acid to gelatin, and stir in a water bath 

 until dissolved ; then add the alcohol and filter. Spread on slide with 

 fine needle. 



F. S. Newcomer, M. D., Indianapolis, Ind. » 



13. What is the best bleacher for diatoms to be used when 

 boiling ? 



Deflagrate with potassium nitrate (saltpetre) in small quantities at 

 a time. Sulphate of potassium and pure diatoms will be left. The 

 sulphate can easily be washed away with water. 



F. S. Newcomer, M. D., Indianapolis, Ind. 



14. What is the best method of eliminating flocculent 

 matter from diatoms after boiling ? 



For large forms boil in pure soap; let diatoms settle and pour off 

 soap and water. For small forms I prefer aqua ammonia. 



F. S. Newcomer, M. D., Indianapolis, Ind. 



15. What is the best bristle for picking diatoms ? 

 I prefer a cat's whisker. 



16. What diatomaceous material is most easily cleaned, 

 and where found ? 



Of fossil earths, perhaps Cherry Hill, Me., or electro-silicon, a 

 polishing powder found at the stores. Prof. H. C. Smith's method of 

 boiling in soap and water is all that is needed. X. 



