84 H. F. Blanford — Description of a rain-gauge with [No. 2, 



The instrument proposed by Mr. Hutchins consisted of two cylindrical 

 vessels of equal size, vie., 8 inches diameter, one three times as deep as the 

 other,* which were to be buried side by side in the ground. The deeper 

 which was to receive the rain, was surmounted by a funnel of the usual char- 

 acter, also 8 inches in diameter ; having a small hole at the bottom, through 

 which the rain should run into the receiver. The other, which was to 

 serve as an evapometer, was closed by a conical cover with a small hole at 

 the apex ; and over this was supported a second conical cover of the same 

 diameter, leaving an interspace of about 1 inch, through which the vapou r 

 might diffuse and escape around the edges. Both were to be padlocked, to 

 prevent any vitiation of the results, by unlicensed interference, on the part 

 of any too curious enquirer. 



Before having the instrument constructed, I slightly altered the 

 design, by reducing the size of the outer or protecting conical cover of the 

 evapometer, and surrounding both the receiving cylinders with a second 

 outer cylinder, in order to protect the upper part of the receiver more 

 effectually against direct heating by the sun. The instrument, thus modi- 

 fied, is represented in the accompanying figure ; it was made at the Mathe- 

 matical Instrument department and in March 1880 was set up at the Alipore 

 observatory ; (buried in the ground, in the immediate neighbourhood of the 

 5 inch Symons gauge, which serves for the daily measurement of the rainfall. 



At the beginning, 4* inches of water, as measured in the measure-glass, 

 for the 8-inch gauge, was placed in the evapometer, and an equal quantity 

 in the receiver of the gauge, (in order to provide for evaporation in antici- 

 pation of rain). At the end of a month, the water in both cylinders was 

 measured ; and the difference taken as representing the rainfall of the 

 period. Four inches of water was then replaced in each cylinder, and the 

 instruments were closed and left untouched for another month. 



Thus the rainfall collected in the new gauge was measured once a 

 month only, while that in the smaller Symon's gauge was measured daily ; 

 and as this comparison was carried on throughout the rains and the subse- 

 quent fine and cold season, the new form of gauge has been fairly tested. 

 The results are given in the following table ; the rain of both gauges having 

 been carefully measured, and the accuracy of the measuring-glasses verified 

 by weighment of their contents. The small corrections, resulting from 

 the verifications, have been applied to the figures in the table. 



* In the drawing sent one was 20 inches the other about 7 inches in height. 



