OMBROMETER. 21 



tube is soldered ou the lower part of the former and encloses the 

 neck of the latter. The funnel and bottle are placed in a box 

 or small cask e, e, sunk to the level of the ground, which is 

 covered with a board d, d, having a circular hole in its centre to 

 receive and support the funnel. To prevent the rain-drops which 

 may fall on this board from spattering into the mouth of the 

 funnel, some pieces of old cloth or carpet, c, c, may be tacked 

 upon it. 



The object of placing the receiving ring so near the surface of 

 the earth, is, to avoid eddies caused by the wind, which might 

 disturb the uniformity of the fall of rain. 



In the morning, or after a shower of rain, the bottle is taken 

 up and its contents measured in the graduated tube f, and the 

 quantity in inches and parts recorded in the register. The gage, 

 or tube, which was first provided for this purpose, will contain, 

 when full, only one-tenth of an inch of rain, the divisions indi- 

 cating hundredths and thousandths of an inch. As this, how- 

 ever, is found to be too small for convenience, another gage, 

 which will contain an inch of rain, and indicating tenths and 

 hundredths, will be sent to observers. 



Another and simpler form of the gage has since been adopted 

 by the Institution and the Patent Office, to send by mail to dis- 

 tant observers. It is one of those which have been experimented 

 on at the Institution, and is a modification of a gage which was 

 received from Scotland, and which has been recommended by 

 Mr. Robert Russell. 



It consists of — • 



1. A large brass cylinder a, b, c, d, two inches in diameter, to 

 catch the rain. 



2. A smaller brass cylinder e, f, for receiving the water and 

 reducing the diameter of the column, to allow of greater accu- 

 racy in measuring the height. 



3. A whalebone scale s, s, divided by experiment, so as to 

 indicate tenths and hundredths of an inch of rain. 



4. A wooden cylinder w, w, to be inserted permanently in the 

 ground for the protection and ready adjustment of the instru- 

 ment. 



To facilitate the transportation, the larger cylinder is attached 

 to the smaller by a screw-joint at e. 



