151 



The fact or difficulty to be dealt with is that the quantity of 

 water delivered over a weir or through a pipe or any other kind of 

 aperture constantly varies with depth or pressure of the head of vater 

 whence it is derived. 



For instance, the quantity of water which is delivered through a 

 four-inch pipe with two feet of water above the orifice will be 354 

 gallons per minute while the quantity delivered through the same 

 pipe with a head of one foot of water would be only 250 gallons per 

 minute, being a difference of 1,240 gallons per hour. 



So the problem to be solved was to invent or arrange some plan 

 by which the water should always be delivered under the same pres- 

 sure which would be secured if always the same head or depth could 

 be maintained. 



In Italy this water measxirer is called a module. The principle of 

 which is, that a stone trough is filled from the canal, river or spring, 

 in which trough or module the water is always kept at one state of 

 fulness or level, and so maintains the same pressure and consequently 

 delivers exactly the same quantity of water at all times and in perpetuity. 



In the United States of America the law of water delivery pro- 

 vides for the construction of a " module. " 



Water is sold by the square inch, that is the quantity which will 

 be delivered by each square inch of the aperture through which the 

 water flows. An orifice one foot long and two inches high, thus 

 delivering 24 inches. 



The law provides that " water sold by the inch by any individual 

 or corporation shall be measured as follows, to wit, every inch shall 

 be considered equal to an inch square delivery orifice under a five-inch 

 pressure, and the five-inch pressure shall be from the top of the orifice 

 of the box (module) to the surface of the water." This will give a 

 constant pressure of four inches. 



A module thus constructed, and with this pressure, will deliver 

 through every square inch of the orifice 7^ galhms (Imperial) every 

 minute, and 450 gallons per hour. 



A four-inch pipe under the same pressure will deliver 94 gallons 

 per minute. 



183. -A JAMAICA DRIFT FRUIT- 



In Nature of November 21st 1895, Dr. D. Morris, Assistant 

 Director of the Royal Gardens, Kew, discusses the origin of a drift 



