2<U rilK AMKHKWN MONTHLY [Sopt., 



luirposi' it is essential that its rcfnu-tivc iiulcx should coiiu-ido 

 as nearly as possible \Yith that of the lenses with which it comes 

 in contact, and it is usually ncccessary to condcns(> the oil to 

 fonie extent. Schiminers ordinary cedar-wooil oil is sUited to 

 have a refractive index N.D. l.oOSGT at 17° which becomes N.I). 

 l.')l(iS'2 when the oil is condensed. — PhaniiaccuticnlJou nvd. 



Muller's fluid. — Ecpial i)arts bichromate of poUissium and 

 of sulphate of sodium dissolved in water, say 2 j^rammes of 

 each salt to 1,(>(H) cc. water, make the best jirescrvativc for speci" 

 mens. It sliould be changed daily tit first and biweekly after. 



MICROSCOriCAL MANIPULATION. 



Cleaning Microscopic Slide and Cover Glasses. — In- 

 stead of warming the slides one by one over a tlaiuf. pushinjj; ofl' 

 the covers, then scrajiin^' away the balsam and cleaning,' with al- 

 cohol, put all your slides together in a saucepan with a lump of 

 washing soda and boil them. The heat of boiling is enough to 

 soften most cements and all ordinary resins used for mounting, 

 and then take out the slides one by one, push ott" the cover- 

 glasses, and put them back. The action of the soda is to con- 

 vert the balsam or other resin into a grumous mass, which is 

 easily wiped off with a little rinsing. Cover-glasses can also be 

 preserved for further use in the same way, if desired. There 

 being nothing on the surface of new covers and slides which 

 will resist the action of hot water and soda, this metliod is prefer- 

 able to the use of strong sulphuric acid, alcohol or the other meth- 

 ods given in the text-books. The exact quantity of soda to be used 

 is immaterial; a j)iece about the size of an egg to half a pint of 

 water will do. 



Solution of Bleached Shellac. — Most of the journals which 

 give directions f(^r dissolving bleached shellac say " soften the 

 shellac by soaking in ether until the gum is swollen, pour off the 

 ether, and add alcohol." The person who tries this will find 

 himself ai the end with a large ]»roportion of undissolved shellac. 

 If, however, he takes the precaution to allow the softened shel- 

 lac to stand awhile, after pouring off the ether, until all of the 

 later not taken up by the shellac has evaporated, and then to 

 use absolute alcohol as a solvent, there will be but little undis- 

 solved shellac. 



