THE FROST AND DKOlMiHT (>K 190.'). DOANE. 



02 9 



The iiupiii'tauc'c of possi'ssiuo a I'cliablc and (*<iuipletc recoinl 

 of rainfall appeals iiioro stroiigh- to tiie municipal engineei" 

 than to any other, because drainage and water-systems and 

 water-power eonstrnction recpiire for tlu'ii- fun<lainental basis a 

 reliable record of rainfall npon which the calcuhitions for his 

 desiffn niav be based. In the design of drainage works the 

 mea'n fall is not the conclusive fundamental datum of the 

 engineer, not even the maximum yciarly fall, but th(> heaviest 

 daily fall, and, more particnlarly, the greatest heaw fall in a 

 short period. The value of having such rec<u'ds from self- 

 recording instruments is two-fold. First, thev give an exact 

 indication of the carrying powers of existing sewers; second, 

 they show the demands likely to be made upon sewers and form 

 a valuable basis upon which calculations for the improvement 

 of existing or the design of new sewers can be based. A single 

 gauge is not always reliable for the measurement of the rain- 

 fall in any gathering ground as instances are reported of a 

 variation of 50 per cent, in one year where gauges were only 

 one-quarter of a mile apart. 



The following fonn of record would be most valuable to 

 the municipal engineer : — 



The rain gauge used by the city of Halifax is of brass, 

 cylindrical in fomi, with a knife-edge rim. The diameter is 



