172 SUMMARY OF CUKRENT RESEARCHES RELATING TO 



to warrant the trouble, it can, of course, be recovered by distillation. 

 The same result may be obtained by shaking up a thin solution of 

 dammar with zinc oxide. The latter should be dropped into a bottle 

 dry, and allowed to settle spontaneously. It carries down with it 

 the suspended particles of dust upon which the turbidity of the 

 solution depends. 



Repairing Balsam Preparations.* — When balsam preparations 

 have been made with a very thin solution, or with a small amount of 

 fluid, evaporation sometimes causes the balsam to be invaded by air- 

 spaces which it is difficult to refill, even with a thin solution of balsam. 

 Such spaces Prof. E. L. Mark finds may readily be filled with the 

 solvent of the balsam (benzol), and then a drop of thin balsam placed 

 at the edge of the cover-glass will gradually replace the benzol as 

 it evaporates, without leaving air-spaces. To prevent a too rapid 

 introduction of the benzole, it is desirable to transfer it with a glass 

 tube drawn to capillary fineness at one end, rather than with a glass 

 rod. If the tube is not too large — 5 or 10 mm. — and is drawn out 

 quite gradually, enough benzole may be sucked into it to serve for 

 repairing a large number of slides without danger of loss by its 

 running out or by evaporation when the tube is laid down. The 

 application of the capillary end of the tube to the edge of the cover- 

 glass induces a steady and even flow of the fluid, until the space 

 beneath the cover-glass is completely filled. 



Arranged Diatoms.f — Mr. C. Febinger, who has made some 

 excellent arranged mounts, uses as an adhesive material to hold the 

 diatoms when placed in position, gelatin (the best photographer's) 

 dissolved in six times its weight of glacial acetic acid. This should be 

 done in a porcelain capsule with a water-bath. When the solution is 

 complete, add one part of alcohol to every fourteen parts of the solution 

 and filter. It is spread on the slide with a glass tube or needle. 



Gold-plated Diatoms. — Mr. A. Y. Moore has now gold-plated some 

 diatoms, but we have not heard whether they show any practical 

 advantage over the slides of silvered diatoms which he recently 

 produced. 



Test Diatoms.— Amphipleura pellucida and A. Lindheimerii.— 

 Mr. J. Deby sends the following note : — " Don Alfredo Truan y 

 Luard, in his. very interesting and well illustrated ' Ensayo sobre 

 la Synopsis de las Diatomeas de Asturias,' gives full instructions 

 for collecting, selecting, and mounting diatoms, and much original 

 matter relating to the microscopical examination and study of the 

 Diatomaceae. The fact to which I wish, however, particularly to draw 

 attention is his having discovered in the north of Spain, abundantly, 

 as he states, Amphipleura Lindheimerii, a species hitherto known 

 only from South America. In a footnote, the author states that 

 Herr Moller of Wedel has asked him for a number of these diatoms, 

 to be mounted by him as test objects. Now A. Lindheimerii is larger 

 and has very much coarser striae, easy of resolution, yet non-specialists 



* Amer. Natural., xix. (1885) p. 1137. 



•j- St. Louis National Druggist, viii. (^1885) p. 196. 



