178 OBSERVATIONS ON THE FALL OF RAIN. 
a map, furnished by the Ordnance office, is 2036 
statute acres. On this area, 250,865,600 cubic 
feet would be equal to a depth of water gathered 
to the reservoir of thirty-four inches in the year, 
besides that required for evaporation from the 
surface of the water. If the fifty millions feet in 
the reservoir were added to the quantity actually 
discharged, the depth would be about forty-one 
inches. 
These observations were apparently taken from 
the summer of 1835, to the summer of 1836, the 
quantity of rain falling during that period, being 
rather under a general average. At Bolton, it 
was three inches less than Mr. Watson’s ten 
years’ average of 49.2 inches.* 
In a report, dated June 30th, 1837, Mr. 
Ashworth states, that during the preceding year 
of 365 days, (probably to midsummer of 1837,) 
289,404,000 cubic feet of water had been dis- 
charged. This quantity would be equal to a 
depth of thirty-nine inches, collected in the 
reservoir. 
* Memoirs of the Literary and Philosophical Society of 
Manchester, volume VI., new series, p. 586. 
