308 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



strip of mica and then burn them, avoiding the great annoyance of 

 having a cover-glass, diatoms and all, slide or fly off. The mica 

 being thin and a poor conductor of heat, the end may be brought to a 

 red heat almost instantly. Now place a glass slip on the turntable, 

 and make a dot or a small circle in the centre as a guide for placing 

 the diatoms. Turn the marked side down, and with gelatine or other 

 material size the spot over the dot or circle ; then with scissors cut 

 from the film of mica a small piece from the best part of the diatom 

 field, moisten the other side and lay it on the glass slide near the 

 marked centre. A crescent-shaped piece may be cut, if desired, that 

 may extend partially around the marked spot. The mica being thin, 

 the focus of low powers need not be changed while transferring the 

 diatoms from the mica to the slide, and one trial will demonstrate 

 that it is much easier to pick from mica than from glass ; also that 

 there is less danger of having the mica fall from the slide while at 

 work. Those who desire to make the arrangement on a cover-glass 

 can do so by placing a cover over the marked centre, sizing it, and 

 then transferring to the cover instead of to the slide. 



Mounting Diatoms in Series.* — P. Francotte uses Threlfall's 

 method f for arranging diatoms in series. The solution of caoutchouc 

 being poured upon the slide, the benzine evaporates, and the diatoms 

 are arranged ; it is then slightly heated, and the diatoms sink into the 

 layer of caoutchouc, where they remain definitively fixed, and can be 

 covered with a thin glass coated with balsam. 



Synoptical Preparation of Pulverulent Objects (Diatoms from 

 Guano, Fossil Earths, &c.). J — P. Barre describes as follows his 

 process of making these preparations, which enable specimens of dif- 

 ferent pulverulent objects to be compared. 



After covering one of the surfaces of a cover-glass with balsam 

 in the manner described for arranging diatoms, § and heating it until 

 the hardened balsam no longer contains any trace of chloroform, the 

 cover-glass is placed in the instrument fig. 42, A. a is a plate of 

 brass, • 75 mm. in thickness. 6 is a strip of steel, fixed at e to the 

 plate a, and to which is riveted another brass plate c. To the latter 

 are soldered nine copper tubes, made as thin as possible (1/5 or 

 1/6 mm.) These tubes pass through the plate c, and project about 

 1 mm. from its under surface. The tubes are of exactly the same 

 length, so that the cover-glass, covered with hardened balsam, meets 

 all the nine tubes at once. 



The plate a has a rectangular aperture d (indicated by dotted 

 lines), and exactly opposite to the orifices of the nine tubes in the 

 plate c. 



The cover-glass is placed between a and the tubes, the surface 

 covered with balsam being in contact with the nine tubes. 



This operation complete, a copper or steel wire, or even simply an 



* Bull. Soc. Belg. Micr., x. (1884) p. 65. 



t See this Journal, iii. (1883) p. 600. 



X Bull. Soc. Belg. Micr., x. (1883) pp. 16-18 (1 pi.). 



§ See this Journal, iii.(1883) p. 453 (I pi.). 



