1032 



RECORD OF CURRENT RESEARCHES RELATING TO 



scientifically. The slides are preparer! under the superintendence of 

 Mr. F. Meyer of Leipzig, who at Dr. Dohrn's request undertook this 

 department. They are of the ordinary English size, and their price 

 varies from 1 to 10 francs. 



Aeroscopes.* — In his studies on the microscopic organisms con- 

 tained in the atmosphere, M. P. Miquel describes two forms of 

 aeroscopes in use at the Montsouris Observatory for collecting such 

 organisms. 



M. Miquel objects to Dr. Maddox's " aeroconiscope," f that the 

 quality of air passing during each experiment cannot be calculated, 

 so that the statement of the number of germs collected has no definite 

 signification. In his opinion, it is preferable to make use of apparatus 

 capable of acting in all weathers, during rain and squalls as well as in 

 fine weather. 



Fig. 105 represents his " aeroscope a aspiration," which is composed 

 essentially of two parts — the bell A, which is solidly fixed at 2 metres 

 from the ground, and the cone B, which is screwed to A. The former 

 has an aspiring tube placed in communication with a trumpet, and the 



FiQ. 106. 



Fig. 105. 



latter has at its upper part a very fine aperture, by which the air is 

 directed to the centre of a thin glass plate smeared with a mixture of 

 glycerine and glucose. This plate, which is kept in a horizontal 

 position, may be brought nearer to the summit of the cone, or vice 

 versa. The air aspired by the trumpet, after having passed through 

 the apparatus, is received in a meter, which measures its volume 

 exactly. 



A second instrmnent (" aeroscope a girouette ") is shown in Fig. 106. 

 It operates by the action of currents of air, and is used only to 

 analyze the air qualitatively when the other form cannot be employed. 

 Like the apparatus of Drs. Maddox and Cunningham, it is light and 

 portable, but in the same time gives 100 times as many germs. It is 

 in the form of an S, and consists of the chambers B (united to a 

 vane, so that the upper bell-shaped aperture is kept constantly 

 opposite to the wind), and A carrying a thin glass plate and a conical 



* ' Brebissonia,' ii. (1880) p. 147. 

 t ' Mod. Micr. Journ.,' June, 1870. 



