J. LeConte— Formation of the Coast Range of Calfornia. SOI 



striking resemblance to impressions of the trunks of Lepidoden- 

 drids. In other cases when greatly elongated they looked like 

 parallel flattened root-fibers. The material of the nodules was 

 similar to that of the containing clay, unless perhaps a little 



A few months afterward, March, i875, in company with a 

 party of students and graduates of the University, I examined 

 the coal mines^ of Mt. Diablo, and there also observed, in the 

 roof of the seam, flattened nodules of sandstone often sur 

 rounded with a thin layer of coaly matter; but the sandstone 

 was coarse and the nodules were imperfect Subsequently Mr. 

 Christy, an assistant in the chemical laboratory, who is now 

 engaged in an examination of the coals of this coast, visited the 

 same mines more extensively and brought me some very fine 

 specimens of flattened elongated nodules. In these also I am 

 assured the long diameters were in the direction of the dip. 



Now, there cannot be the slightest doubt that these nodules 

 were once day pelkis, of all sizes, from that of swan shot to 

 that of hazel nuts, which existed in, and on the surface of, the 

 original clay sediments, having been taken up from finer de- 

 posits rolled along by gentle currents and deposited along with 

 coarser material, precisely as we find at the present day ; and 

 further, that their present shape is due wholly to subsequent 

 pressure, precisely as in the case of the greenish elliptical 

 spots found in cleaved slates, and described by Prof: Tyndall:* 

 and, therefore, finally, that by means of their shape and posi- 

 tion, as in the case of the greenish spots, it is quite possible to 

 determine the amount of mashing together in one direction 

 and the extension or upswelling in another, which the sedi- 

 mentary mass has suffered since its deposition, 



I take the case of the Hay ward seam as the simplest becans.- 

 the .strata are vertical. Taking three e^?/^? rectangular diam- 

 eters of the original unmashed pellets, one in the direction vi 

 pressure, i. e., horizontal and at right angles to the strata ; another 

 also horizontal but in the direction of the strike, and the third 

 in the direction of the dip or vertical, it is evident that the 

 first would be shortened, the third would be elongated, while the 

 second would, on the average, be unaffected, since extension of 

 this diameter in some places must be compensated by shorten- 

 ing in contiguous places right or left We may assume, there- 

 fore, that the elongation vertically is strictly correlated with the 

 mashing or short'enins horizontal! v, and the one is a measure 

 of the other. Now I found by careful measurement of a great 

 number of these nodules that the shortest diameter bears to 

 the longest the ratios of 1:3, 1:4, 1:6, 1:9, and ev( n 1 : 12 

 and 1 : U. I believe a fair average would be about 1 : 6 or 



