HOW TO STUDY METEOROLOGY. 
141 
but that methodical common-sense which every fairly educated 
person is presumed to possess. 
A rain-gauge is a contrivance for ascertaining how much rain 
falls on a particular surface of ground — to what depth it would 
accumulate if it neither ran away nor soaked in. With any 
cylindrical vessel and a foot-rule, a notion of the quantity of 
rain that has fallen can be arrived at, but this involves accidental 
errors, owing to evaporation, and to the difficulty of seeing, to a 
nicety, how deep the rule has to be plunged into the collected 
water. Fig. 1 represents a cheap and convenient gauge, known 
as Howard’s. It consists of a metal funnel, the rim of which is 
accurately turned to a certain diameter (usually five or six inches)* 
The rain, passing through the funnel, is collected in the earth- 
enware receiver. The receiver is emptied once in twenty-four 
hours, the contents being poured into a graduated glass. The 
diameter of the glass is so adjusted* to the diameter of the 
funnel, that a certain vertical height corresponds to a certain 
depth of fall, and the divisions are marked accordingly. Usually 
matters are so arranged, that a glass, eight inches high, shall 
contain half an inch of rain ; this permits the divisions, each of 
the value of T -^oth of an inch, to be tolerably far apart. 
Another rain-gauge in common use is represented by Fig. 2. 
It is heavier and more expensive than Howard’s, but may be a 
fixture, inasmuch as the water is drawn off from the tap below, 
and, by the glass tube, analogous to that used to indicate the 
quantity of water in a steam boiler, the amount of rain collected 
can be ascertained by inspection. The employment of this gauge 
has no other advantage than a slight saving of trouble, an insuf- 
ficient compensation for the increased cost. A third very com- 
mon gauge is represented by Fig. 3. It seems scarcely necessary 
to explain the engraving. 
The site selected for a rain-gauge is a matter of some moment 
— 1st, as to elevation : It is well known that, according as a gauge 
is near the ground, or fifty feet above it, the rain collected will 
differ by a large amount. One foot above the surface will be 
found a reasonable height ; that clears the splashing from the 
soil, and as the gauges are usually made about a foot high, its 
base then rests on the actual ground. — 2nd, as to surrounding 
objects: The gauge must be placed in as open a situation as 
possible — fifteen or twenty feet away from any wall or shrub — 
and a greater distance still from a house or tall trees. 
There is a diversity of opinion as to whether observations 
should be made (1) at 9.0 p.m. and entered as belonging to 
the same day, or (2) at 9.0 a.m. and entered as belonging to 
* For the practical object I have now in view, it is needless to say more on 
this subject. 
