4 Prevention of Street Floods 



of rain falls per minute, or in a given number of minutes, 

 during a rain-storm ; and I am, therefore, unable to speak 

 with certainty of the maximum height to which the water 

 has risen in the shortest time. 



I can only speak of results, without being able to trace 

 the element of time so accurately as I could wish, and as it 

 is of the utmost importance to ascertain the largest quantity 

 of water that falls in a given time, I have designed a self- 

 registering rain-gauge, that will give the information I 

 require. Possibly and probably I might be able to obtain 

 the information from the Government Observatory, where 

 there may be instruments that register the quantity of 

 water falling per minute. If so, our President will be 

 able to inform me ; if not, I will endeavour to have one 

 constructed as follows : — 



For strict accuracy and facility of calculation I would 

 make the area of the rain-gauge 100 inches, or a square of 

 10 inches ; the rain falling upon this would pass into a 

 vessel mounted upon a spring balance, that would indicate 

 the weight of water as it fell ; then, by having a disc of 

 paper or an endless web driven by clockwork and divided 

 into minutes by radiating or lateral lines, a small spring 

 pencil would inscribe the weight of the water each minute 

 as it fell, and a properly calculated table would show the 

 quantity, and that with an accuracy, notwithstanding the 

 friction of the pencil (which would be almost a constant 

 and could be allowed for), that has seldom or ever been 

 hitherto obtained, that is so far as I am aware of. The 

 same end might be accomplished by a float, &c, but for 

 accuracy I would prefer the spring-balance. However, as I 

 may make this instrument and the result of the experiments 

 with it the subjects of a short paper at some future date, 

 I will not further intrude upon your time by giving a more 

 detailed description of it ; but will conclude my remarks, by 

 observing that the records of such an instrument, if it exists 

 or can be made, will be of signal service in determining the 

 size of drains or culverts requisite for the discharge of 

 storm- waters from any giving area. 



Ke verting to the heavy rainfall of the 11th February, 

 1857, 1 have calculated that the total that fell upon the 956 

 acres forming the water-shed draining through the city, was 

 nearly 74 millions of gallons, or over 330 thousand tons ; and 

 that, of this quantity more than 38 millions of gallons or 

 170,000 tons fell upon the area drained by Elizabeth-street 



