TILE AND PIPE DRAINING. 107 



of Mr. Hammond s farm, recording the facts, that, after a rain of 

 about twelve hours duration, on the 7th, I found the drains, on 

 the 9th, in a nine-acre piece, three feet deep, just dribbling, and 

 those in a hop-ground adjoining, four feet deep, exhausted ; Mr. 

 Hammond having observed, previously to my arrival, that the 

 greatest stream at the outfall of each drain amounted to about 

 the half-bore of the inch pipe.&quot; 



u The rain-gauge informs us that ^^ of an inch in depth of 

 rain fell upon each square foot of surface in the observed time 

 of twelve hours. This quantity is equivalent to 69-Jj cubic 

 inches, or 2j- pounds, which, divided by twelve hours, gives 

 little more than T 2 cr of a pound per square foot of surface per 

 hour for the weight of the rain.&quot; 



&quot; The drains were 24 feet asunder, and each pipe a foot in 

 length, so that each lineal foot had to receive the water falling 

 on 24 square feet of surface, equal to 60 pounds, or 6 gallons ; 

 and as the time which this quantity occupied in descending 

 through the soil and disappearing was about 48 hours, it results 

 that 1^ pounds, or one pint per hour, entered the drain through 

 the crevice existing between each pair of pipes. Every one 

 knows, without having recourse to strict experiment, how very 

 small a hole will let a pint of water pass through it in an hour, 

 being only one third of an ounce per minute, or twice the con 

 tents of a lady s thimble.&quot; 



&quot; The weight of rain, per acre, which fell during the 12 

 hours, amounted to 108,900 pounds, or 48 T 6 &amp;lt;j tons, which on the 

 whole piece of nine acres, is equal to 437 T 4 g- tons ; and each 

 drain discharged 19 tons, equal to about ^ of a ton per hour, on 

 the mean of 48 hours ; but when the flow was at the greatest, I 

 find that each drain must have discharged at the rate of five 

 times this quantity per hour, which affords proof of the faculty 

 of the pipes to receive and carry off a fall of rain equal to 2- 

 inches in 12 hours, instead of half an inch a fall which is 

 quite unknown in this climate. Half an inch of rain in twelve 

 hours is a very heavy rain. I learn from Mr. Dickinson that 

 his rain-gauge has never indicated so great a fall as l.i inch in 

 24 hours, and from Dr. Ick, the curator of the Birmingham 

 Philosophical Institution, that only on five occasions has the 

 rain there exceeded one inch in 24 hours, during the same 

 period of eight years. We may, therefore, consider the fact of 



