" Great inconvenience arises among engineers and hydraulicians, from the want of a standard unit, to denote the quantity of water flowing in a given time. The fountaineer's inch (pouce d> eau de fontainier) is used by all French writers upon the subject, though admitted by most of them to be very indefinite. It is perhaps sufficiently correct for practical purposes, but not adopted in philosophical investigation. Genieys says, it is equal to the quantity of water a pipe an inch in diameter would furnish in a minute, so (

placed that the centre of orifice should be seven lines below the surface of the reservoir to which it is adapted. To estimate the quantity it is still necessary to determine the length of the pipe or thickness of the side of the vessel in which the aperture is made, through which the water is discharged. Now this has never been done in such a way as that all agree upon the exact amount but it is generally admitted to be equal to 15 ;

pints, or 13.33 litres a minute, or 19,195 litres in 24 hours.' " The above are French measures. The litre is equivalent to 61,028 cubic inches ;

hence the fountaineer's inch is 813 1-2 cubic inches a minute, or 678 cubic feet a day. Gallon, as used by English writers, is also a very ambiguous term, when applied to hydraulic discharges. The gallon which I employ in this report,= 231 cubic inches the ;

beer gallon,= 282 and the imperial gallon,= 277,274 cubic inches. ;