18 



OMBEOMETER. 



top rising above the ground about three inches; cover it witt 

 boards slightly inclined in the form of a roof, which project on 

 all sides beyond the edge of the barrel at least a foot. A cir- 

 cular opening in the middle receives the funnel, the borders of 



^"'^^^B^VN^^' 



which rest on the board. At the bottom of the barrel, to receive 

 the water, is an earthen or metallic vessel, with a narrow neck, 

 (an ordinary earthen jug will answer,) in which is placed the 

 end of the funnel, exactly filling the opening. It must contain 

 iwo or three quarts. The funnel is fastened by means of two 

 clasps to the board, which must be covered up with sod, to make 

 it like the ground itself. If circumstances render it necessary to 

 place the ombrometer higher, the height must be carefully noted 

 la the journal. If it is placed upon a sloping roof, it should be 

 ou the top, and not at the edges, or at the angles, and must be 

 raised several feet above the roof itself. 



Observation. — To make the observation, remove the funnel, 

 and pour the water from the jug into the large graduated glass 

 cylinder. The opening of the funnel being one hundred square 

 inches, one inch of rain in depth gives one hundred cubic inches 

 of water ; and each division of the glass containing a cubic inch 

 of water, each of them represents a hundredth of an inch of rain 

 fallen into the ombrometer. These degrees are large enough to 

 permit us to estimate the thousandths of an inch. The divisions 

 of the smaller graduated glass cylinder will measure directly the 

 thousandths of an inch, and it may serve, in case of accident, as 

 a substitute for the larger one. The two glass vessels may be 



