190 



University of California. 



[Vol. 2. 



further comment. In a foot-note in the above-mentioned descrip- 

 tion * the writer mentions the occurrence of rolled pebbles near the 

 southeastern end of the island, at altitudes of 1,000 and 1,400 feet, 

 but considers their character doubtful. It is possible that these 

 rolled pebbles are not shore deposits, but it seems now to the 

 writer hardly probable, especially in the case of those at the 1,000- 

 foot level, which rest on a terrace-like portion of one of the branch 

 ridges running from the main ridge. This branch ridge and the 

 others near it have a roughly terraced character at several points. 

 On the ridge where the pebbles were found, such benches occur at 

 800 feet, 1,000 feet, and 1,060 feet. The 1,060-foot bench is one of 

 the most pronounced of these, and it agrees pretty closely with the 

 altitude of the corresponding notches on the neighboring ridges. 

 As determined by a hand-level, this bench was a very little lower 

 on the ridge to the north, and a little higher on the ridge 

 to the south, than on the ridge where the pebbles are. On 

 another minor ridge about a mile to the south of this, notching was 

 seen at the altitudes 865 feet, 1 ,060 feet, 1,300 feet, and 1,400 feet, 

 as determined by aneroid. These benches are not very pronounced, 

 especially as they occur on sharp ridges where they would more 

 readily suffer obliteration than on little dissected surfaces. It is of 

 course possible that some of these readings do not represent defi- 

 nite former ocean levels, but, taking all the evidence into considera- 

 tion, it is improbable that some of them are not true terraces. 



Further evidence to the same end is to be found in the plana- 

 tion of the summit of the island (in addition to the terracing of the 

 Little Harbor region, already mentioned). This character has been 

 ascribed by the writer f to peneplanation ; but more mature con- 

 sideration has convinced him that it could be due neither to pene- 

 planation nor primarily to beveling^, but that it must have been 

 caused mainly by marine abrasion during a depression of the island, 

 and after the present topographic forms had been largely developed. 



* Loc. cit. , p. 12. 

 t Loc. cit., p. 69. 



JSee, Tarr, The Peneplain, Am. Geol. Vol. XXI, June, 1898, pp. 351-370, 

 and, Smith, Some Aspects of Erosion in Relation to the Theory of the Pene- 

 plain, Bull. Dept. Geol., Univ. Calif., Vol. 2, No. 6, 1899, p. 162. 



