ZOOLOGY A.ND BOTANY, MICROSCOPY, ETC. 835 



with a plane surface. The operator must be cautioned not to use iron 

 wire, which rusts so rapidly that it will soon throw down a flocculent 

 precipitate. Another good plan, which is perhaps the better of the 

 two, is to siphon oflf the water until only a sufficient quantity remains 

 to permit the sediment to be shaken up with it, and poured into a tall 

 conical glass, from which, after standing again for a short time, por- 

 tions may be taken up by means of a pipette, and placed on slides for 

 examination. If the subsidence is observed to be complete, it is rather 

 an advantage to have a good body of water in the glass, or, at least, so 

 much as will permit the pipette to be used with ease and facility. It 

 may be observed here, that it is very inconvenient to have too much 

 fluid at a time on a slide. The cover-glass will be unstable and liable 

 to have its upper surface wetted, while the objects themselves will be 

 tremulous, if they do not quite run out of the field. To obviate this, 

 the pipette, when taken out of the water, should be held in a vertical 

 position for some little time, until the suspended matters gravitate to 

 the bottom of the tube, when a well-charged droplet might be placed 

 on a number of separate slides and examined seriatim. This is, in 

 fact, the only way in which a large sediment can be thoroughly 

 inspected. 



M. Balland also gives* a neat and easy method for examining 

 water contaminated by the drainage of cesspools. Into a long tube 

 he pours a few cubic centimetres of a solution of sodium hypobromide, 

 and then fills it completely with the water to be examined. Placing 

 the thumb on the tube, it is inverted and placed in a glass containing 

 mercury. If urea is present, bubbles of nitrogen gradually rise in 

 the tube and collect at the closed end. 



J. W. Mallet describes f apparatus whereby the water to be 

 examined may be evaporated under greatly reduced pressure and at a 

 correspondingly low temperature, out of contact with the air. Under 

 such conditions, the organic matter is altered much less than in the 

 apparatus generally made use of. As test-materials, leucine and 

 tyrosine were selected, as representing the more stable products of 

 putrefaction liable to occur in natural water, and for which the com- 

 bustion process in its natural form had been found to give results far 

 from satisfactory. 



Mr. G. E. Davis has also published J two articles on ' Water, 

 Water Analysis and the Microscope.' 



Changing the Water in Aquaria containing Microscopical 

 Organisms. § — F. Konike describes the following as the more con- 

 venient way for emptying aquaria without drawing away the minute 

 organisms : — 



Tie over a small flask or glass, with the widest possible mouth, 

 a piece of fine muslin in such a manner as not to stretch it 

 tight. Then put the end of an indiarubber tube through the middle 

 of the muslin to the bottom of the glass. At the place through 



* Journ. do Pharm. et de Chimie, 1883. Cf. ' Athenaoum,' 24th Nov., 1883. 

 t Chem. NewH, xlvii. (1883) pp. 218-20, 232-3, 

 X Micr. News, iii. (1883) pp. 30D-I3 (7 figs.). 

 § Zool. Anzeig., vi. (1883) pp. 638-9. 



