ISOSTASY 571 
Mr. Lewis suggests more than once in his article that possibly 
the existing condition is “‘an over-compensation at a greater depth 
for land areas with probably complete compensation for ocean 
areas’? or ‘“‘under-compensation at a shallower depth for land areas 
with complete or over-compensation for ocean areas” (p. 626). 
If Mr. Lewis or anyone else will carefully test these ideas in 
the manner indicated on pp. 563-70 of this rejoinder he will cer- 
tainly reach the conclusion that there is nothing in the suggestion. 
The writer had made such tests, and others, before Mr. Lewis’ 
article was written. 
To test such suggestions by complete computations, such as 
those set forth in Hayford’s publications which are under criticism, 
would be a waste of time. It is not worth while to spend months 
in testing a suggestion by a complete computation if, as in this 
case, a rough test made in one or two days will show the sugges- 
tion to be in error. 
Turn now to another direct and positive statement made by 
Mr. Lewis, which is closely allied with the questions discussed 
above. After stating, correctly, that all Hayford’s principal 
computations were made on the assumption that the isostatic 
compensation is complete, Mr. Lewis continues thus (pp. 610-11), 
“This was a purely arbitrary assumption on Hayford’s part since 
he gave no reason whatever for believing at the outset that com- 
pensation is complete, and furthermore the fact that he later 
attempts to find the degree of completeness implies that there is 
no reason to believe at the outset in complete compensation.” 
Hayford has indicated in various places in his publications 
that gravitation tends to produce a readjustment of the material 
composing the outer portion of the earth toward the condition 
of approximate equilibrium known as isostasy." 
Gravitation acts continuously. It certainly tends to produce 
complete compensation. Is it purely arbitrary to assume complete 
compensation as a first approximation? The writer believes it 
is not. 
t Consult especially The Figure of the Earth and Isostasy, pp. 66-67, 166-68, and 
the Minneapolis address referred to in the first paragraph of this rejoinder. In this 
address the possible mechanics of the readjustment is indicated. 
