ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 709 



a few seconds ; the slip being correspondingly heated, the specimen is 

 pressed home on the slip, taking care to exclude all air-bubbles. As 

 each slide is dealt with it is placed on a second plate of glass (3£ by 

 1\ in. by f\ in. thick, the blocks being strictly uniform) and heated to 

 melt the beeswax, which is used to hold the slip in position during its 

 subsequent treatment. After the entire series has thus been treated and 

 allowed to cool, each glass plate or block in turn is clamped in the special 

 holder, and the slicer passed through the rock close to the glass of the 

 mounting slip. With everything in good order this may be done to 

 within 0*5 mm. ; the thickness being regulated by means of two strips 

 of thin sheet iron, held in position on the slip while the cut is being 

 started. 



The series having been sliced, each section is ground to within 

 O'l mm. on the coarse grinding lap, using F carborundum, or certainly 

 not a coarser grade than 220. After washing, the grinding is completed 

 on the finest revolving lap, and if the latter is true and the operator 

 experienced scarcely any further grinding will be required. With a 

 sufficiently finely-graded powder, there should be no scoring or scratches ; 

 the latter, if present, being due to fragments of too coarse a powder, or 

 to its use in too limited a quantity, thus allowing the specimen to come 

 in contact with the metal of the lap. As a rule, and for safety, it is 

 wiser to give the last touches by hand upon a suitable lap of slate or 

 glass, using only the finest washed powder. 



The whole process is not so long or so complicated as any description 

 must necessarily seem to imply. With the aid of the machine described, 

 and given balsamed slides in readiness, I find it possible to complete 

 single slides in 10 to 15 minutes ; the finished section, in area, uni- 

 formity, and thinness, leaving little to be desired. Furthermore, with 

 a series of rocks — and it is usual to treat a number together — there 

 is a corresponding gain in time, throughout the several operations. 

 Naturally, too, and perhaps more particularly with the type of machine 

 just described, individual experience, dexterity of manipulation, and judg- 

 ment, are material factors affecting the final result, both as to time and 

 quality of work. Compared with the older type of machine, both hand 

 and treadle, there can be no question as to the net gain in time and 

 labour, both of which are important. There is, too, I think, an equi- 

 valent improvement in the average quality of the finished product. On 

 these grounds I hope the publication of this brief description will prove 

 useful to all who are interested in the preparation of rock-sections." 



(4) Staining- and Injecting-. 



Staining Bordered Pits.* — G. Kowallik used three solutions : 



(1) 1 grm. acid-fuchsin dissolved in 100 grin. 95 p.c. alcohol and filtered ; 



(2) 1 grm. anilin-green (brillant-griin ?), obtained from Wolff of Posen, 

 dissolved in 100 grm. of distilled water and filtered ; (3) 1 grm. chryso- 

 idin dissolved in 100 grm. 95 p.c. alcohol and filtered. Sections of 

 Pinus hardened in alcohol are covered with solution (2) and the slide is 

 heated to vaporization. After a minute the slide is washed in water and 

 then treated with solution (3) diluted one-half with water. After allowing 



* Zeitschr. wiss. Mikrosk., xxvii. (1911) pp. 26-7. 



