22 



L. CASELLA'S CATALOGUE 



FIG. 63. 



FIG. 68. 



FIG. 65. 



KAIN GAUGES. 



The increasing importance attached to a knowledge of rainfall, as well as evaporation, 

 in various localities, has for some time contributed to the exercise of considerable skill 

 in arranging the most suitable instruments for these purposes. The instruments, how- 

 ever, being simple in themselves, the great question was, as to the most desirable size, 

 as well as height, from the ground on which they should be placed, large areas as a 

 rule obtaining the preference. In an extended series of careful experiments, however, 

 liberally conducted by Colonel Ward, at his own expense, and assisted by that eminent 

 authority on rainfall, Mr. Symons, it was found that the best sizes were between five 

 and eight inches of circular area ; Mr. Glashier, F.K.S., then President of the Meteorolo- 

 gical Society, also preferring the latter size, the following are made according to this 

 result. The height again is fixed at ten to fourteen inches above the surface of the 

 ground, the rain caught decreasing in quantity in proportion as gauges are raised above 

 that height. 



62. Rain Gauge (Dr. LIVINGSTONE'S portable), expressly arranged by L. CASELLA for 



the Zambesi expedition, with receiving surface of 3-inch diameter, whereby 

 (See Stratton, " New Edinburgh Philosophical Journal,") the greatest accuracy 

 is obtained, with graduated jar, in maroon case for the pocket 16 6 



63. EAIN GAUGE, as described by Howard in his "Climate of London" (fig. 63), in 



which evaporation is prevented and the rain collected in a stone bottle by a 

 copper funnel of five inches diameter ; turned brass ring, and strong glass 

 measure divided to 100th of an inch depth of rain . . 15 6 



