, if this gives the maximum thrust for the coherent earth.
Turning now to pressures on tunnels, the writer is pleased to note that Mr. Meem has recorded some more of his experiences concerning them. From lack of proper knowledge of the so-called constants,
,
and
, such experience is an aid in leading to more probable values.
As the writer proceeds in this investigation, he hopes to make clear the conception of arch action alluded to, and will derive the limiting values of
