DISCUSSION : FORESTS, RESERVOIRS, AND STREAM FLOW 475 
in spite of all his tables and plausible arguments, the upshot would be mr. Chitten- 
that, if the “sports” or “freaks” (the extreme low waters) are taken 
care of, navigation will accept the inconveniences that may come from 
any possible increase in frequency of lesser low waters? 
At the risk of repetition, the writer will notice also Professor 
Swain’s remarks in this connection. He says: “A few great, but not 
extreme, floods may do more damage than one extreme flood, and may 
necessitate more expenditure for dredging and other purposes.” Pro- 
fessor Swain is a teacher in one of the leading technical schools of the 
world. Undoubtedly, he inculeates the habit of clear statement and 
the avoidance of loose generalities in speech on the part of his pupils. 
But he has violated the most elementary principles upon this subject 
in the proposition quoted above. What is an extreme flood, and what 
a great flood? Has he any clear distinction in his own mind? And 
are causes that operate to produce an extreme flood any different from 
those in a great flood? The only possible construction to place upon 
the above statement is that forests produce a beneficial effect upon 
floods up to a certain limit, and after that the reverse effect. Professor 
Swain can hardly wish to stand sponsor for any such theory as that. 
Again, what would be the practical bearing of the theory, if it were 
true? In carrying out works of flood protection, if the conditions of 
the extreme flood are met, all others are included; but if only some 
lesser floods is considered, then the great floods remain uncontrolled. 
Now it is of course true that a sufficient number of smaller floods may 
do as much damage as one very great flood; but, as a general rule, the 
damage wrought by floods increases very rapidly with their height, and 
if Professor Swain places a wide limit between his extreme and his 
great floods it is doubtful if all the latter, on any river that may be 
considered, cause the amount of damage that the former do. But 
manifestly the subject, as stated by Professor Swain, is altogether too 
indefinite to base an opinion upon, one way or the other. 
Mr. Leighton and Professor Swain will inevitably find, when it 
comes to a practical application, that they cannot get very far away 
from the writer’s statement that “it is the extreme of flow * * * 
that controls the cost of river regulation. It is the floods and low 
waters that measure the cost. Any scheme of control that is not based 
upon these is worthless.” 
The writer now withdraws his momentary acceptance of Mr. 
Leighton’s theory, and challenges his statement that his tables prove 
“beyond controversy the increase in floods due to deforestation.” His 
theory was first given prominent publicity by Dr. W J McGee in a 
speech before the Ohio Valley Improvement Association, in Louisville, 
in October, 1908, in which he presented a table, reproduced here as 
Table 18. The last two columns have been added to show the stages 
used by Dr. McGee to denote his floods and the danger line stages that 
are usually considered as defining real floods: 
