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SOME NOTES ON LOCAL RAINFALL. 46 
and from which it runs through a funnel into the cylinder. In the 
cylinder there is a float suspended by a brass wire, working over a 
pulley inside the cylinder and passing through a hole in the side of 
the cylinder and over another pulley outside. The wire carries a pen 
carriage and pen. The pen is adjusted so as to mark upon a recording 
drum. This drum is carried on a vertical rod forming a pivot, and is 
actuated by a pinion wheel and ratchet gearing, the pinion being 
revolved by clockwork. The gearing is so proportioned as to revolve 
the recording drum once every 24 hours, The receiving cylinder is 
fitted with a tap for drawing off the rainwater, and when the instru- 
ment is in use the paper diagram upon which the rainfall is recorded 
is fitted round the recording drum, so that, at the time of adjustment, 
the pen point is upon a particular horizontal line of the diagram in 
a position corresponding with the time which is marked in hours and 
is indicated by vertical lines on the diagram. 
The action of the instrument is as follows :—Rain falling in the 
gauge is conducted into the receiving cylinder, raising the float 
and lowering the pen correspondingly. Meantime the recording 
drum is being revolved by the clockwork gearing. The result is a 
line drawn by the pen upon the diagram in a more or less sloping 
direction from right to left according to the rate and duration of the 
rainfall. When there is no rain the line drawn by the pen is hori- 
zontal. It should be particularly observed that the diagram is not 
distorted or exaggerated, and consequently the record is not capable 
of very minute analysis. ‘The instrument is not of very delicate 
construction, being designed for practical purposes. Should a very 
accurate record be required, it would, of course, be a simple matter 
to render the instrument more delicate in its action, by reducing the 
diameter of the receiving cylinder and float, and increasing the 
distance between the horizontal lines on the diagram correspondingly, 
in order to obtain an exaggerated diagram, showing two or three 
or more times the actual depth of rainfall, as may be desired. 
For the purposes of this paper I have adopted an empirical 
standard forheavy rain of aquarter-of-an-inch (*25)of rain per 24 hours. 
