PREFACE TO SECOND EDITION 



AFTER fifteen years of use in his classes, the author has been 

 enabled to prepare a second edition of this little book, partly 

 for the purpose of correcting certain minor errors and partly 

 that certain additional material might be inserted. 



In recent years a great deal of attention has been given to 

 the careful analysis of the problem of rainfall and run-off; notably 

 by Messrs. Grunsky, Gregory and Nordell, and only after much 

 hesitation was it decided to omit any extended review of their 

 thorough, detailed discussion. The relation between rainfall 

 and run-off is dependent upon many very uncertain factors, and 

 any close mathematical analysis of the way in which water, 

 delivered to any area as rain, is collected into one channel 

 at a single point of the area must include so many assumptions 

 that the result may be far from the truth, although correct 

 according to the theory followed. It was decided, therefore, to 

 again follow the method of Kuichling, adopted in the first edition, 

 as being reasonably safe in principle and at the same time 

 holding clearly before the student the chief factor that enters 

 into the relation, viz., the impervious character of the surface 

 on which the rain falls. Reference is made, however, to the more 

 mathematical treatment, and anyone interested may consult 

 the original papers if he so desires. 



The use of better jointing material for vitrified pipe has 

 made it possible to eliminate leakage entirely, if sufficient care 

 be taken in construction. Various asphaltic preparations and 

 other patented articles are on the market and if properly used 

 will ensure a perfectly water-tight pipe line. This fact modifies 



