962 



SCIENCE. 



[N. S. Vol. XXIII. No. 600. 



eonfming hills, and these have a very 

 straight trend; in some places, however, it 

 passes over mountain ridges, usually, at 

 the divide separating the ends of two val- 

 leys ; it even in some eases goes over a spur 

 or shoulder of a mountain. Along this 

 line are very commonly found abrupt 

 changes in the normal slope of the valley 

 sides giving rise to what are technically 

 known as scarps. These scarps have the 

 appearance of low precipitous walls which 

 have been usually softened and rounded 

 somewhat by the action of the weather. 

 Small basins or ponds, many having no 

 outlet, and some containing saline water, 

 are of fairly frequent occurrence and they 

 usually lie at the base of the small scarps. 

 Trough-like depressions also occur bounded 

 on both sides by scarps. These troughs 

 and basins can only be explained as due to 

 an actual subsidence of the ground or to 

 an uplift of the ground on one side or the 

 other, or on both sides. The scarps sim- 

 ilarly can only be ascribed to a rupture of 

 the earth with a relative vertical displace- 

 ment along the rupture plane. Frequently 

 small knolls or sharp little ridges are found 

 to characterize this line and these are 

 bounded on one side by a softened scarp 

 :and separated from the normal slope of the 

 Talley side by a line of depression. In 

 many cases these features have been so 

 modified and toned down by atmospheric 

 attack that only the expert eye can recog- 

 nize their abnormal character; but where 

 their line traverses the more desert parts 

 of the Coast Range, as for example in the 

 Carissa Plains, they are well known to the 

 people of the country and the aggregate 

 of the features is commonly referred to as 

 the 'earthquake crack.' 



This line begins on the north at the 

 mouth of Alder Creek near Point Arena 

 and extends southeasterly nearly parallel 

 with the coast line to a point about two 

 miles below Port Ross, a distance of forty- 



three miles. Here it passes outside of the 

 shore line and is again met with at the 

 point where Bodega Head joins the main- 

 land. Thence it appears to continue south- 

 ward through Tomales Bay and Bolinas 

 Lagoon. Beyond Bolinas Lagoon it passes 

 outside of the Golden Gate and enters the 

 shore again at Mussel Rock, eight miles 

 south of the Cliff House. From this point 

 it is traceable continuously along the val- 

 ley line occupied by San Andreas and 

 Crystal Springs Lakes, past Woodside and 

 Portola, over a saddle back of Black Moun- 

 tain, thence along Stevens Creek Caiion, 

 passing to the southwest of Table Moun- 

 tain and Congress Springs to the vicinity 

 of Wrights, on the narrow-gauge railway 

 between San Jose and Santa Cruz. From 

 Wrights it continues on in the same course 

 through the Santa Cruz Mountains to the 

 point where the Southern Pacific Railway 

 crosses the Pajaro River near Chittenden. 

 From the crossing of the Pajaro the line 

 extends up the valley of the San Benito 

 River, across the eastern portion of Mon- 

 terey County, and thence follows the north- 

 eastern side of the valley of the San Juan 

 River and the Carissa Plains to the vicin- 

 ity of Mount Pinos, in Ventura County. 

 The line thus traced from Point Arena 

 to Mount Pinos has a length of 375 miles, 

 is remarkably straight, and cuts obliquely 

 across the entire breadth of the Coast 

 Ranges. To the south of Mount Pinos the 

 line either bends to the eastward following 

 the general curvature of the ranges or is 

 paralleled by a similar line offset from it 

 en echelon; for similar features are re- 

 ported at the Tejon Pass and traceable 

 thence though less continuously across the 

 Mojave Desert to Cajon Pass and beyond 

 this to San Jacinto and the southeast 

 border of the Colorado Desert. The prob- 

 ability is that there are two such lines, 

 and that the main line traced from Point 

 Arena to Mount Pinos is continued with 



