342 Transactions of the Society. 



This plan was adopted instead of the bladder with siphon suspended 

 beneath the base board, to hold the water supply. The box can be 

 easily made of a length and size to hold the aeroscope, bladders, and 

 tubes, for easy carriage. I tried suspending a bladder contained in 

 a calico sac, for the sake of lessening the weight in the place of the 

 metal box, but gave the preference to the box for the reasons given. 

 With this simple form of aeroscope I have drawn over 460 measured 

 ounces of air by seven ounces of water. Details have been dwelt 

 upon, so that any one, after obtaining a proper funnel of glass, 

 metal, or metal enamel-covered, can easily construct the rest. Care 

 must be taken to see that the sticky material used does not contain 

 any microphytes, or the results will be falsified. The tripod is not 

 even a necessity, as by a little ingenuity the parts of the apparatus 

 can be otherwise held in position. Careful regulation of the water- 

 flow is necessary to obtain the greatest quantity of air sucked 

 through the aeroscope by the least quantity of water. To increase 

 the length of the fall tube, it was wound round one of the legs of 

 the tripod, but without advantage, as friction appeared to delay the 

 flow. The thin covers with the dust collected are placed down on a 

 clean slide for microscopical examination. 



