12 On a New Form of 



Art. Y.—On a Neio Form of Self- Registering Rain-gauge. 

 By R L. J. Ellery, F.R.S., &c. 



[Read 16th May, 1878.] 



For the ordinary purpose of rainfall observation and 

 record, the common rain-gauge, where the rain collected is 

 measured in a graduated glass measure once or twice a day, 

 is all that is required. 



Questions often arise, however, in which the rate at which 

 heavy rains fall, or the time over which the fall may he 

 spread, becomes an important point, and this is especially 

 the case in cities, large towns and other localities, in connec- 

 tion with drainage, disposal of storm waters, &;c. To meet 

 such requirements a self-registering rain-gauge, that will 

 furnish the required information, becomes a valuable and 

 indeed an essential instrument. 



Various forms of self-registering rain-gauges are con- 

 structed, the best of which are very expensive, while the 

 cheaper ones are generally very defective and untrust- 

 worthy. 



The form I now submit to the Society can, I think, claim 

 simplicity and economy in construction, a high sensitiveness 

 as well as trustworthiness. 



The principle is this. The rain which is collected in a 

 circular area of 10 in. diameter flows at once through the 

 pipe into (G), a small copper vase-shaped vessel (E E) holding 

 about 19 "5 cubic inches of water. This vessel is suspended 

 from an iron bracket by two steel spiral springs (F) made of 

 the best pianoforte wire, and most carefully tempered. In- 

 side this vessel is a small glass tube, bent into the form of a 

 siphon (S), and projecting through the bottom for about 10 

 or 12 inches, forming an intermittent siphon, which, when- 

 ever a certain quantity of water has accumulated, 

 rapidly empties the vessel. This acts so delicately 

 that it always requires the same quantity, almost to a 

 single drop, to cause it to overflow, and it will always 

 overflow with this exact quantity. In this gauge it 

 empties itself for every quarter of an inch of rain collected 

 in the receiver — that is, when about 19*5 cubic inches (= J 

 of an inch fall) have accumulated. As the rain drops into 

 the vessel from the receiver the suspending spiral springs 



