434 JOURNAL OF THE PLYMOUTH INSTITUTION, 
hours of January Ist, 1875.* It may convey a better idea of what 
I mean when I speak of an inch of rain, if I state that it means 
22°687% gallons, or 1014 tons of water per acre ; 7.e. nearly 65,000 
tons of water precipitated on every square mile of surface; or, 
again, one inch of rain means more than 5 Ibs. 3 oz. on every 
square foot of surface on which the rain falls ; and therefore in a 
room of the size in which we now are, an inch of rain would 
measure 567 gallons, that is, more than 103 hogsheads, and weigh 
2 tons 104 cwt. 
I have already spoken of the sheltered position of my gauge, 
and to get as nearly correct returns as lay in my power I have 
consulted other observations made in the town, and find that in 
the ten years from 1869 to 1878, both inclusive, Mr. Balkwill, on 
the top of his house in Old Town Street, collected 412-05 inches 
against 363°19 collected in my gauge; he thus showed a rainfall 
of 13:45 per cent. greater than I did. The elevation of his gauge 
(35 feet) above the street necessarily gave him too little. I then 
took the five years from 1870 to 1874, and found that at Drake’s 
reservoir Mr. Bellamy collected 201°43 inches, against 196-94 by 
Mr. Balkwill, and 171:09 by myself. Thus it would seem my 
returns should be increased by 17°73 per cent., or about by one- 
sixth for rainfall, and the number of rainy days by 3°47 per cent., 
* We subjoin a table of all rainfalls greater than an inch for the last 
decade :— 
inches inches 
February 7, 1870 . ' . 1°31 | September 17, 1875 2 > thee 
May 12, 1870 ; ; . 1°16 | September 21, 1875 ; witPat 
July 10, 1870 ; ; ¢.,1:20:| October: 18,,1875.4, 7 » ol D2 
July 29, 1871 > 9: » 91:04 |, October 26, 1875 (eu emma 
August 17, 1871 . 2 . 1:00 | August 4, 1876 . : + anus 
June 18, 1872 ; : . 1:04 | September 29, 1876 ? oo 
July 6, 1872 ; ; . 1°35 | December 26, 1876 ; : (rea 
January 26, 1873 . ; so 2137} Aprils, 1877 : ‘ - 1°45 
July 25, 1873 ; ; . 1°46 | August 26,1877 . : . mae 
November 5, 1873. ; . 116 | January 2,1879 . ; 2 ee 
January 8, 1874 . : . 1.07 | June 30, 1879 ; ; pe be 
September 3, 1874. . . 1:27 | August 19,1879 . : . #1 OU 
September 30, 1874 ' . 1:12 | September 18, 1879 ; «> 128 
January 1, 1875 . ; . 2°15 | October 25, 1879 . : s) 12a 
July 14, 1875 , ; . 1°91 | July 25, 1880 . . « saa 
It would thus appear we may expect a rainfall of an inch or more five 
times in two years. 
