CHAP. II.] WATER SUPPLY. 43 



birds an opportunity of bathing, in which they delight ; 

 but they will soon splash out all the water from that, 

 and therefore a reservoir with a narrow opening is more 

 sure to satisfy the wants of the community. It is best 

 to provide one of each. Of the latter kind none can 

 be preferable to that described in the " Treatise," af- 

 fording, as it does, opportunity for a lecture on Hydro- 

 statics. 



" The water-bottle should be a large glass bottle with 

 a long neck, holding four or five gallons (the carboys, 

 in which various fluids are received by dispensing che- 

 mists, are very suitable for the purpose), and its belly 

 made in the form of an egg, to keep them from dung- 

 ing on it ; but the shape is not material, as a piece of 

 paste-board, hung by a string at three or four inches 

 above the bottle, will always prevent that, by hindering 

 them from settling thereon. This bottle should be 

 placed upon a stand, or three-footed stool, made hollow 

 at top to receive the belly, and let the mouth into a 

 small pan ; the water by this means will gradually de- 

 scend out of the mouth of the bottle as the Pigeons 

 drink it, and be sweet and clean, and always stop when 

 the surface of the water meets with the mouth of the 

 bottle. 



" The reason of which is evident ; for the belly of the 

 bottle being entirely close at top, keeps off all the ex- 

 ternal pressure of the atmosphere, which pressing hard 

 upon the surface of the water in the pan, which is con- 

 tiguous to that in the bottle, is too potent for the small 

 quantity of air which is conveyed into the belly of the 

 bottle with the water, and which consequently, as being 

 the lighter matter, rises to the top of the bottle, as it 

 stands in its proper situation; but the water being 



