ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 361 



/3. Collecting, Mounting, and Examining Objects, &c. 



Aeroscopes. — Dr. E. L. Maddox comments upon the remarks of 

 M. Miquel on this subject,* particularly in reference to his statement 

 that his aeroscope a girouette gathers 100 times more germs than the 

 aeroconiscope Dr. Maddox used in 1870. 



The aeroconiscope was not exposed, as supposed by M. Miquel, for 

 the entire twenty-four hours, except in one case, but was removed 

 during rain and at night, except on one other occasion when it was 

 left exposed for eighteen hours. Tabulating the total number of hours 

 for the several daily exposures in the diiferent months, the result is as 

 follows : — 



April 19 — Exposures 1.57 hours, against total time, 456 hours. 

 ' ■ „ „ 556 „ 



652 „ 

 456 „ 

 240 „ 

 1) )> 528 „ 



624 „ 

 „ „ 165 „ 



The position of the apparatus was much sheltered, especially by 

 the houses, from the more prevalent winds, S.S.W. and W. The 

 garden was surrounded by a wall and contained many trees. The 

 small village lay chiefly at the back of the house, north and east, a 

 brewery being at a considerable distance away. The house faced a 

 large open field, with the Solent beyond, the town of Southampton 

 being at some distance on the north and north-west. The instrument 

 was also coarsely made, the funnels being of tin, so doubtless many 

 particles were arrested on their path to the thin cover-glass. 



The enumeration was leal, and made immediately upon the thin 

 cover being removed, and not by comparison of the relations between 

 the surface of the exposed gathering- glass and the field of the Micro- 

 scope. Moreover, neither pollen nor starch grains were counted, 

 which enter into M. Miquel's category, to be allowed for by a per- 

 centage which, to be correct, should vary according to the season ; for 

 in summer we may expect more pollen, and in the chief brewing 

 months more cells of yeast and starch from the breweries of a large 

 city. May there not also be some doubt, Dr. Maddox asks, of the 

 correctness of M. Miquel's method of calculating the results of the 

 exposures of forty-eigJtt hours, for is it not possible that many yeast- 

 cells and small torulae may within that period, on warm moist days 

 especially, develope, and the attempt to distribute the dust equally 

 throughout the sticky material used, by means of a needle-point, be 

 liable to detach or disjoint the newly formed or secondary cells, and 

 thus add directly to the original number for calculation '? 



No doubt in strong winds many of the lighter particles are carried 

 much higher than the level of the instrument ; nor is there any possi- 

 bility of obtaining exactness unless by using an aspirator that could 

 draw through the instrument a column of air of a given height, always 

 turned to face the wind ; for if the velocity of the latter exceed the 



* See this Journa], Hi. (1S80) p. 1032. 



