1855] WRITINGS OF JOSEPH HENRY. 3 



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. Should 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 con- 

 siderable space also around the mouth of the funnel should 

 be kept free from plants — as weeds or long grass, and the 

 ground should be so level as to prevent the formation of 

 eddies or variations in the velocity of the wind. 



Measuring snow. — To ascertain the amount of water pro- 

 duced 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 perpendicu- 

 larly into the snow until it reaches the ground, or the top 

 of the ice, or last preceding 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 measured as so 

 much rain. When the snow is adhesive, the use of the tin 

 plate will not be necessary. 



From measurements of this kind, repeated in several places 

 when the depth of the snow is unequal, an average quantity 

 may be obtained. As a general average, it will be found 

 that about ten inches of snow will make one inch of water. 



