1054 SUMMARY OF CURRENT RESEARCHES RELATING TO 



coil, SO as to contain a mucli larger percentage of ozone than any 

 natural atmospheric air, was passed continuously through a 1 per 

 cent, solution of white of egg placed in a glass flask, the inlet and 

 outlet tubes of which were carefully plugged with cotton-wool 

 previously to commencing the experiment. It was found that a 

 stream of air, containing an amount of ozone equal in weij^'ht to the 

 albumen in solution, passed through 100 c.c. of the liquid for thirty 

 hours, failed in producing the slightest trace of oxidation, and that 

 the ozonized air passed through the liquid quite unaltered. During 

 the course of the experiment and for six days following, the develop- 

 ment of micro-organisms ceased, but at the end of that time, and not- 

 withstanding the cotton-wool plugs, the liquid became slightly turbid 

 from the presence of organisms. As dilute hydrogen peroxide is 

 without action upon albumen, the conclusion seems inevitable that 

 albumen is practically indestructible by any atmospheric agency 

 without previous splitting up by micro-organisms, and further, that 

 whilst micro-organisms cannot develope and are probably killed in an 

 ozonized atmosphere, their spores are not easily destroyed by its 

 agency. These results confirm the surmise of tlje late Dr. Angus 

 Smith, that putrefaction is a necessary preliminary to oxidation in all 

 cases oi natural river purification. 



MICEOSCOPY. 

 a. Instruments, Accessories, &c.* 



D'Arsonval's Water Microscope. — Our justification for noticing 

 this instrument (fig. 229) is that it has been suggested by a leading 

 member of the Societe de Biologie of Paris, M. D'Arsonval, who 

 presided at a meeting of the Societe in May last. The suggestion is, 

 moreover, evidently a serious one, as the Societe devoted two pages of 

 their Proceedings f to a description of it. 



The principle of the instrument depends upon the fact that if an 

 object is viewed through a parallel plate of glass it will appear the 

 nearer as the plate is thicker. The interposition between the ob- 

 jective and the eye-piece of a greater or less quantity of water will 

 act in the same way, and thus (in theory) a very sensitive method of 

 focusing is obtained, the focus varying according to the thickness of 

 the stratum of water. 



The construction of the instrument is as follows : — A glass 

 cylinder (fig. 230), open at the top and closed at the bottom by a 

 plane glass disc, is inserted into the body-tube, which is split to allow 

 the contents of the cylinder to be observed without removing it. An 

 orifice at the lower end communicates by an indiarubber tube with a 



* This subdivision is arranged in the following order: — (1) Stands; (2) Eye- 

 pieces and Objectives ; (3) Illuminating Apparatus ; (4) Other Accessories ; 

 (5) Photo-micrography ; (6) Manipulation ; (7) Microscopical Optics, Books, 

 and Miscellaneous matters. 



t See this Journal, ii. (1879) p. 767. 



