1899] MICROSCOPICAL JOURNAL. 209 



classified. Some suggestions are made as to the possible 

 explanation they afford of the origin of many of the 

 structural characters of rocks in nature. 



Varnish. — Excellent finishing varnishes may be made 

 by well mixing on glass artists' oil paint with gold size. 

 Only sufficient for immediate needs should be mixed at 

 one time. Sealing wax, dissolved in alcohol, is also use- 

 ful, but only the best wax should be used, otherwise the 

 varnish is liable to chip and leave the glass. 



Washing. — Dr. G. H. Bryan suggests the following de- 

 vice for the more effective preparation of desmids, dia- 

 toms, and other minute mounting material. The removal 

 of all traces of acid necessitates frequent washings and 

 decantations of the residues. It is, therefore, important 

 that the vessel in which these operations are performed 

 should hang vertically, otherwise much of the residue 

 rests against the sides of the vessel and gets carried 

 away during the decantation. Dr. Bryan gets over this 

 difficulty by suspending the test-tube by a U-shaped 

 piece of wire across the base of which an india-rubber, 

 ring is fixed. The test-tube is placed in the ring, the 

 elasticity of which allows the tube to hang perfectly free- 

 ly. The precipitation of the diatoms is hastened if the 

 tube be set swinging slightly. The device will also be 

 found useful for washing andcollecting the insoluble res- 

 idues of limestones and other rocks. 



Cross-sections. — Cross-sections of fibres may be ob- 

 tained by glueing together a mass of the fibre, bedding 

 in paraffin or by rolling them like a cigarette in a piece 

 of sheet wax. When cut, the mass of mixed sections is 

 placed in benzole or alcohol, when the wax soon floats on 

 top and may be poured off. 



Mounting. — The following method of mounting in 

 balsam on the cover, and backing up with black varnish, 

 will be found useful for such objects as foraminifera,min- 

 erals, seeds, etc. Cement a thin glass-cover to a slip by 



