PROCEEDINGS. 
529 
By appointment, the following obituary notices were prepared 
and read: 
Of Peter Parker, by W. B. Taylor, published in this volume, 
pages 491-492. 
Of E. B. Elliott, by Wm. Harkness, published in this volume, 
pages 470-473. 
Of F. V. Hayden, by A. C. Peale, published in this volume, 
pages 476-478. 
Of Roland D. Irving, by I. C. Russell, published in this vol¬ 
ume, pages 478-480. 
Of Thomas Hampson, by H. W. Henshaw, published in this 
volume, pages 474-475. 
Of Emil Bessels, by W. H. Dali, published in this volume, 
pages 465-466. 
Mr. Bailey Willis made a communication on The Mechanism 
of the Overthrust Fault. 
[Abstract.] 
Mr. Willis referred briefly to the views of Professor H. D. Rogers, pub¬ 
lished in 1842, and to those of Professor Heim, of Zurich, published in 
1878 and again in 1888, concerning the formation of faults intimately 
related to folds, which frequently arise in the steeper side of an anticlinal, 
and which may be termed overthrust faults. Professor Heim’s explana¬ 
tion of phenomena of this nature rests upon the fact observed in the Alps, 
that the inverted limb of an anticlinal is stretched or is even crushed 
between the anticlinal and synclinal cores of an overturned fold moving 
in opposite directions. This explanation fails to account for faults in the 
Appalachians, because the essential fact of squeezed beds has not been 
found. 
The Appalachian sedimentary series from Cambrian upwards is com¬ 
posed of strata differing greatly in their capacity for resistance to hori¬ 
zontal thrust. These variations of rigidity occur in the same stratum 
originally in the same horizontal plane, and also in different strata super¬ 
imposed one on the other. It follows that a rigid stratum may not fold 
at the place where a vertically adjacent flexible stratum does fold; the 
rigid stratum may ride forward on its lowest bedding plane until it 
reaches an axis, anticlinal or synclinal, in which both beds have suffered 
flexure. The forward movement will then shear across the beds on the 
opposite dip, producing a fault. 
The facts relating to this hypothesis were illustrated by photographs 
of folded strata and of models; the latter showed differential folding and 
faulting produced in layers of wax by horizontal thrust. 
68—Bull. Phil. Soe., Wash., Vol. 11. 
