31 
EXPLANATION OF PLATE LXXX. 
Fig. 1. Contortion apparatus. 
a. Cylinder containing shot. 
b. Pod connecting a with the vertical plate c. 
d. d. Frame in which the plate c slides. 
e. Knife-edge, hinged on c. 
f. Iron block, sliding in groove h, to which the lamina k is fixed by the 
screw g. 
i. Apparatus for setting the index l at zero in any position of the vertical 
plate. 
l. Index moving over a graduated arc. 
m. Index moving backwards and forwards to show the deviation of e from 
the perpendicular. 
Scale nearly | of the actual machine. 
All the parts are iron or steel, except the cylinder a , the rod b, the indices 
and the scale, which are brass. 
Figs. 2, 3. Examples of distorted pebbles in conglomerate at Newport, 
Phode Island, reduced from Memoirs of the Boston Society of Natural 
History, vol. i. pi. 17, 18. 
