Jotyv—A Fractionating Rain-Gauge. 285 
with air (save for that part of its longer limb dipping beneath the 
water in bottle 1), it remains to consider what will ensue when the 
reservoir is again filled in the progress of the rainfall. This time, 
Diacram oF Fractionatine Rain-GAuGeE. 
when the water begins rising in the siphons, the siphon leading to 
bottle 1 has evidently the hydrostatic pressure due to the depth of 
water covering its exit in bottle 1 opposing its operation. It thus 
