108 



oxygen and hydrogen, but from its property of readily dissolving 

 most of the solids and gases it comes in contact with, pure water 

 does not exist out of the chemical laboratory. 



The purest form of water we meet in nature is the rain as it 

 falls, but even here it is dissolving, in its fall, the gases out of the 

 atmosphere ; and as soon as it reaches the ground and spreads itself 

 on the surface it takes into solution many impurities. 



As the ultimate source of our water supply is the rainfall, it 

 will be of interest just to glance at the meteorological condition 

 of Dover. I must here acknowledge my indebtedness to 

 Mr. W. Thomas, C.E., the Borough Surveyor. If we first 

 take the prevailing winds which bring us our clouds, we shall be 

 able to consider our water supply " ab initio." 



Table shewing the number of days each wind prevailed : — 



We may also remark that in 1893 there were 189 clear days, 

 27 foggy days, and 149 overcast. 



The next table gives the rainfall for the last two years : — 



1893. 



Taking the mean of the two years we shall find that 33-07 

 inches of rain fell annually in Dover. An " inch " of rainfall means 

 of course, that if the rain which fell did not sink into the ground, 

 or evaporate, it would form a pool of that depth over the area 

 indicated. Therefore the rainfall of Dover would represent a pond 

 33 inches deep covering the whole of Dover. The weight of this 

 quantity of water would be immense, for one inch of rain means 

 100 tons of water to the acre. 



