584 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



While the slides are cleaning, the cover-glasses should be soaking 

 in spirit and potash. They may now be removed one by one, and 

 wiped on a rag. If necessary, they can be so treated a second time ; 

 but in either case they are to be dropped while wet into clean water. 

 In removing the covers it will be found that the spirit and potash has 

 decomposed the balsam and any gold-size, black varnish, &c, upon 

 them, and the dropping them while wet into the water prevents the 

 adherence of any particles by the decomposition caused by it. 



Mr. Barnard has tried benzine, turpentine, and many other things, 

 but nothing seems so expeditious and cleanly as the mixture recom- 

 mended, as it frees the slide from grease, which has to be done after 

 using benzine or turpentine. There is a risk in leaving the covers in 

 the bottle of spirit and potash too long, for fear of an injurious effect 

 of the potash on the glass ; but this has not yet happened, though 

 they have been left uncleaned for a long time after being removed 

 from the slides. 



Resolution of Amphipleura pellucida. — Mr. E. M. Nelson 

 informs us that since the date of the December conversazione of the 

 Society he has found that the exhibit he then made of longitudinal 

 lines on Amphipleura pellucida (dry on cover-glass) was an error — the 

 lines then shown were due to diffraction. He has since observed true 

 longitudinal lines on this diatom by a more careful adjustment of the 

 vertical illuminator, and has assured himself that they are finer than 

 the 10th band of Nobert's latest 20-band plate, i. e. finer than 112,595 

 to the inch. The objective was Powell and. Lealand's y 1 ^ homog. imm. 

 ofl-43N.A. 



Repeated countings of the transverse lines on the particular 

 frustule examined show them to be at the rate of 96 in the *001 inch, 

 and therefore capable of resolution by any immersion objective (of 

 sufficient power) whose effective aperture exceeds 1*0 N.A., and con- 

 versely incapable of resolution by any dry lens. 



Microscopic Examination of Wheat-flour.* — C. Steenbuch re- 

 commends the following mode of preparing meal for microscopic 

 examination and determination of the starch-grains, by which the 

 elements of the tissue can be easily isolated. The process depends 

 on the well-known fact that a solution of diastase transforms starch- 

 paste into dextrin and maltose. In order to obtain a solution of 

 diastase, 20 g. of ground meal are placed for an hour in 200 g. cold 

 water and repeatedly shaken, and then filtered through a double 

 filter. 10 g. of the specimen of meal to be examined are then 

 thoroughly mixed with 30-40 g. of cold water, the mixture placed in 

 a beaker, and stirred up with about 150 g. of boiling distilled water. 

 At a temperature of 75°-80° C. the formation of paste begins. The 

 temperature is now allowed to fall to 55°-60° C, and 30 c.cra. of the 

 clear filtered extract of malt added. The mixture is then stirred up, 

 and the temperature kept at 55°-60° in a water-bath for 10 minutes. 



* Ber. deutsch. chem, " Ges., xiv. (1881). See Bot. Centralbl., x. (1882) 

 p. 140. 



