230 



TENTH ANNUAL REPORT OF 



Fig. 11. 



It consists of — 



1. A large brass cylinder a, h, c, 

 d, two inches in diameter, to catch 

 the rain, 



2. A smaller brass cylinder e, /, 

 for receiving the water and reducing 

 the diameter of the column, to allow 

 of greater accuracy in measuring the 

 height. 



3. A whalebone scale s, s, divi- 

 ded by experiment ,so as to indicate 

 tenths and hundredths of an inch of 

 rain. 



4. A wooden cylinder lo, w, to be 

 inserted permanently in the ground 

 for the protection and ready adjust- 

 ment of the instrument. 



To facilitate the transportation, 

 the larger cylinder is attached to 

 the smaller by a screw-joint at e. 



Directions for use. — To put up this rain-gage for use : 1. Let the 

 ■wooden cylinder 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, as shown in 

 the figure, and the arrangement is completed. 



The depth of rain is measured by means of the whalebone scale, 

 the superficial grease of which should be removed by rubbing it with 

 a moist cloth before its use. 



fShould the fall of rain be more than sufficient to fill the smaller 

 tube^ then the excess must be poured out into another vessel, and the 

 whole measured in the small tube in portions. 



Care should be taken to place the rain-gage in a level field or open 

 space, sufficiently removed from all objects which would prevent the 

 free access of rain, even when it is falling at the most oblique angle 

 during a strong wind. A considerable space also around the mouth 

 of the funnel should be kept free from plants, as weeds or long grass, 

 and the ground so level as to prevent the formation of eddies or varia- 

 tions in the velocity of the wind. 



To ascertain the amount of water produced from snow, a column of 

 the depth of the fall of snow, and of the same diameter as the mouth 

 of the funnel, should be melted, and measured as so much rain. 



The simplest method of obtaining a column of snow for this purpose 

 is to procure a tin tube, about two feet long, having one end closed, 

 and precisely of the diameter of the mouth of the gage. 



With the open end downward, press this tube perpendicularly into 

 the snow until it reaches the ground or the top of the ice, or last pre- 

 ceding snow ; then take a plate of tin, sufficiently large to cover it, 

 pass it between the mouth of the tube and the ground, and invert the 

 tube. The snow contained in the tube, when melted, may be mea- 



