66 THE AMEKICAN MONTHLY [March, 



pass into the receiver. The sand, which will form little bars on the 

 glass, must be removed occasionally, and it gradually creeps towards 

 the lower end of the glass, and there would eventually pass into the 

 receiver. 



The loss of diatoms will be very small. Usually one pouring is 

 sufficient for cleaning. The sand can be rewashed if necessary, or a 

 little clear water run over the sand on the glass strip will carry forward 

 almost the last diatom ; but this will scarcely pay for the trouble. A 

 short piece of glass will cause a failure, and too great an incline w^ill be 

 found almost as had.— J^ourn. JV. T. Micr. Society., v. (1889), p. 116. 



A New Method of Finishing Balsam Mounts.* 



By F. N. pease, 



ALTOONA, PA. 



It is only a question of time when balsam mounts thoroughly hard- 

 ened and unprotected from atmospheric influences will be ruined, on 

 account of the cover-glass becoming detached, especially during rough 

 handling. Discoloration of the mounting medium often occurs pre- 

 vious to the more serious result above mentioned, proceeding from 

 the margin inward. On the other hand, preparations in which the bal- 

 sam, storax, or other resinous media are used, are often injured by the 

 running in of the cement used for finishing the slide, when sufficient 

 care is not taken. 



A method has been adopted, which effectually obviates these objec- 

 tions, and at the same time renders it possible to mount and finish a 

 slide at once, without the delay due to allowing successive coats of 

 cement to dry before others are applied. The mounts need not be 

 thoroughly hardened before finishing, provided the nature of the prep- 

 aration does not require it. 



The method used is as follows : The object is mounted on the slide, 

 applying the cover-glass in the ordinary manner, using either balsam, 

 hardened balsam, balsam and benzole, storax or damar. The slide 

 is then heated to drive off" the solvent, or more volatile constituents, 

 either gently in a water bath or at a higher heat, even boiling care- 

 fully over a spirit lamp when the nature of the object will permit. 



When cold, the superfluous mounting medium when present, is care- 

 fully removed, then a narrow ring of paraffine wax is applied in the 

 following manner : Hard white paraffine wax (such as is used for im- 

 bedding) is heated in a suitable capsule until it is melted and quite 

 limpid. With the aid of a very small camel's-hair pencil, the melted 

 paraffine is applied at the edge of the cover-glass, covering the exposed 

 mounting medium and instantly solidifying. With round cover-glasses 

 and a turn-table, very neat narrow rings of paraffine wax can be readily 

 and rapidly applied. Whenever they are not satisfactorily symmetri- 

 cal, a penknife may be used to bring them to the desired shape. 



It is now necessary to apply a finishing cement. For this purpose 

 Bell's cement has been found excellent, when modified as described 

 below. 



*From the Microscopical Bulletin, 1890. 



