1879.] 815 [Wadsworth, 
and elongations of pebbles were to be seen. The subject was also 
earlier discussed by Professors Niles and Shaler and Dr. Jackson. 
(Proc. Bost. Soc. Nat. Hist. xv, 1-3). 
The attention of American geologists was first called (so far as I 
am aware) to this subject by Professor Edward Hitchcock in 1859, in 
a paper presented to the American Association at the Springfield 
Meeting (Proc., x11, 355), entitled, “On the Conglomerate near 
Newport, R. I., with elongated Pebbles and transverse Joints.” ‘This 
paper was not published. My experience with this subject has been 
limited, but such as it is, it would lead to the conclusion that 
many of the cases relied upon to prove the indentation, flattening, 
and bending of pebbles after their deposition have been misinterpre- 
ted. It was my fortune in the summer of 1874 to accompany the 
Assistant Geologist of the New Hampshire Survey for some weeks in 
the survey of that state. This gentleman, from his association with 
Professor Charles H. Hitchcock, was an enthusiastic believer in the 
plasticity and distortion of conglomerate pebbles, and pointed out 
numerous examples of their supposed occurrence. Not one of these 
examples seemed to me to sustain either the premise or conclusion, 
the form being such as can be seen any day on the beach where 
pebbles of like lithological character occur. In the summer of 1877 
the locality pointed out by Professor Vose was visited, but nothing 
was found to sustain the arguments or conclusions of his paper. 
Since that time microscopic sections of the slates and so-called con- 
glomerates mentioned by Mr. Wm P. Blake as sustaining his conclu- 
sions have been examined by me. These are from the Sierra 
Nevada, and are designated in his paper as ‘‘ gravestone slates.” To 
the eye the so-called “conglomerate made up of flattened pebbles,” 
appears to be composed of a detrital mud holding fragments of argil- 
lite. Microscopic examination shows that the rock is composed for 
the most part of diabase detritus. The crystals of augite remain 
very perfect in most cases, and no mark of distortion by pressure was 
seen anywhere. ‘The evidence is very strong that this was deposited 
as a mud flow. While in general the longer axis of the fragments 
and crystals is parallel with the lines of flow, many examples of 
crystals and fragments arranged at all angles were seen. As far as 
can be told by a microscopic examination of Mr. Crosby’s “ pinite 
schist,” it is the same as, or similar to, the Californian rock spoken of 
above. From the specimen exhibited I hardly think any mineralogist 
would call the fragments serpentine, neither is it evident that any 
g 
On page 315, fourth line from bottom, for microscopic read 
macroscopic. 
