2 WRITINGS OF JOSEPH HENRY. [1855 



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 may be tacked upon it. 



The object of placing the receiving ring so near the sur- 

 face 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 

 belonging to the apparatus, and the quantity in inches and 

 parts recorded in the register. The tube or gage which was 

 first provided for this purpose will contain when full only 

 one-tenth of an inch of rain, the divisions indicating hun- 

 dredths and thousandths of an inch. As this however is 

 found to be too small for convenience, another gage — which 

 will contain an inch of rain, and indicating tenths and hun- 

 dredths — will be sent to observers. 



Another and simpler form of the gage has since been 

 adopted by the Institution and Patent Ofiice, to send by 

 mail to distant observers. It is one of those which have 

 been experimented on at the Institution, and is a modifica- 

 tion of a gage received from Scotland, which was recom- 

 mended by Mr. Robert Russell. 



It consists of — 1. A large brass cylinder, two inches in 

 diameter, to catch the rain: 2. A smaller but longer brass 

 cylinder for receiving the water and reducing the diameter 

 of the column, to allow of greater accuracy in measuring 

 the height : 3. A whalebone scale divided by experiment, so 

 as to indicate tenths and hundredths of an inch of rain: 4. 

 A wooden cylinder to be inserted permanently in the ground 

 for the protection and ready adjustment of the instrument. 

 To facilitate the transportation, the larger and smaller cylin- 

 ders are connected together by a screw-joint. 



To put up this rain-gage for use — 1. Let the wooden cylin- 

 der be sunk into the ground, in a level unsheltered place, 

 until its upper end is even with the surface of the earth: 2. 

 Screw the larger brass cylinder on the top of the brass tube 

 and place the latter into the hole in the axis of the wooden 

 cylinder, and the arrangement is completed. 



