142 THE AMERICAN MONTHLY [June, 



glycerine mount, take one of these slides, run a fresh ring over the old 

 and hard one, fill with glycerine (containing the specimen), press down 

 the cover, wipe off the excess of glycerine, ring again, and set aside to 

 dry. 



Another mounting material which could be used with this kind of a 

 cell is carbolized water, which is made by adding to a few ounces of 

 pure water a very small amount, say one-quarter or one-eighth of a 

 drop, of a saturated solution of crystallized carbolic acid in water. 



Another medium for mounting was discovered by Mr. Munn acci- 

 dentally. He had a mount of the buffalo moth and had ringed the cell 

 with Brown's rubber cement. Unfortunately, in one sense, but for- 

 tunately, in another, the cement ran in upon the specimen, when, to Mr. 

 Mann's surprise, the portions touched by the cement appeared to better 

 advantage than the rest of the object. 



In mounting diatoms, he very seldom uses balsam, as there are other 

 media which are better and easier to handle. Among these are sty- 

 rax and tolu. These, as they are purchased in the stores, need to 

 be purified. Styrax can be purified with benzole. Tolu also, which 

 contains the troublesome (because crystallizable) cinnamic acid, can 

 be purified with the same material, which in the cold dissolves cin- 

 namic acid, but not the pure tolu. 



The purified tolu is then poured upon a sheet of glass to allow the 

 benzole adhering to it to evaporate, and afterwards dissolved in chloro- 

 form and filtered. When mounting with this medium there is no 

 trouble with air-bubbles; it seems to be impossible for one to remain 

 under the cover. The mount must be ringed, however, for if not the 

 tolu will creep. Mr. M. uses Brown's rubber cement rubbed up with 

 a little Prussian blue to give it a color. 



Mono-bromide of naphthalene has a high index, but it is hard to 

 confine. A good cement for this mount is Strat^na, which is after- 

 wards covered with gold size or shellac. 



To illustrate the difterence between the appearance of a diatom 

 mounted in balsam and another in mono-bromide, Mr. Mann exhibited 

 two slides of Surrirella cardinalis mounted in these media. The 

 superiority of the mono-bromide mount was seen at once. 



Brightwellia pulchra was then exhibited, mounted in balsam and 

 also in tolu, and the latter shovs^n to be much superior. 



St. Louis Ci>ub of Microscopists. — E. J. Nitzschmann, Sec'y. 



May <5, i8go. — The regular meeting of the Society was held at the 

 College of Pharmacy, and proved a very interesting one. President 

 Falk occupied the chair. Mr. C. C. Faris read a paper on Oil of Tur- 

 pentine used in Microscopy, and the Method of Rectification. Prof. 

 Whelpley gave the result of his examination of lycopodium for adul- 

 terants, but found all of the specimens to be pure. 



Prof Whelpley also read a paper on The Best and Simplest Methods 

 for Cleaning and Repairing Old Mounts. 



The following slides were donated to the cabinet : Blatta orientalis^ 

 by Mr. Goodman ; Ossicles from ear of rabbit and rat, by E. J. Nitz- 

 schmann ; Cannabis indica and section of locust's wing, by C. C. 

 Faris. 



