93 



On some Micro-Cements for Fluid Cells. 



By Charles F. Rousselet, F.R.M.S. 



{Read Jmw 17tJi, 1898.) 



Three years ago I read before you a short note on Clark's 

 Spirit-proof Micro-Cement, which had proved rehable for many 

 years in securely sealing micro cells containing methylated 

 spirit. I then recommended this same cement for cells con- 

 taining watery fluids. It appears, however, that I too hastily 

 jumped to the conclusion that, because this cement is good for 

 spirit mounts, it would also be equally good for watery fluids, 

 a conclusion which seems natural enough. After three years' 

 experience I must pronounce it a complete failure as regards 

 watery fluid mounts, while the spirit mounts remain as good as 

 before ; and I hasten to communicate these facts, so that others 

 may profit by my experience. 



The possession of a thoroughly good and reliable cement for 

 fluid, and especially watery fluid mounts, is so important to 

 microscopists, that I hope all members of the Club who have 

 any special knowledge and experience in this direction will com- 

 municate their experience for the benefit of all. Owing to the 

 failure of the cement to keep in the water, I have had to remount 

 over three hundred slides of Rotifers, which is no small work, 

 attended with considerable risk of losing the objects. I have 

 a few deep cells filled with fluid which have kept very well for 

 four or five years, but it appears the greatest difficulty is met 

 with in small shallow cells, which contain only a fraction of 

 a drop of water. 



I have, of course, continued my search for a cement which will 

 absolutely prevent the evaporation of water. It seems that all 

 cements containing solid particles become porous, or at least 

 slightly pervious to watery vapour, when once quite dry, and 

 therefore it appears to me that one of the objects to be aimed at 

 is to prevent the total evaporation of the solvent. 



