60 SOUTHERN CALIFORNIA GEOLOGY 



Cuyamaca and San Jacinto, it was decided to use those 

 four stations as base stations in comparing the old and 

 the new triangulation in California. In the adjustment 

 of the old work, the geographic positions of Mt. Lola 

 and Round Top and of Cuyamaca and San Jacinto, 

 which resulted from the western net adjustment, were 

 used as bases for the observations of the old triangula- 

 tion. The results obtained would indicate a change of 

 geographic position of about six feet to the southeast- 

 ward for Mt. Tamalpais, nearly four feet northward 

 for Sierra Morena, seven feet southeastward for Loma 

 Prieta, and varying amounts — less than seven feet — 

 for the stations between Loma Prieta and Gaviota. The 

 directions of change in the positions for the intermedi- 

 ate stations are generally southeastward. There is a 

 southeastward movement indicated for stations Mt. 

 Helena, Monticello, Vaca, Mt. Diablo and Mocho, vary- 

 ing from approximately six feet at Mocho to three and 

 one-half feet at Monticello. 



Adjustments are now being made at this office of 

 additional stations such as Mt. Ross, Farallones Light- 

 house and some stations in the vicinity of Monterey 

 Bay. The results are not yet available. 



To the eastward of Gaviota, the differences in posi- 

 tions vary from one foot to five feet. The general di- 

 rection of change is southeastward to the vicinity of 

 the stations Santa Clara and Laguna. There the direc- 

 tion is more southerly and, when we get to Mt. Wilson 

 and the Los Angeles base stations, the direction of 

 change trends to the southwest. 



Since the arc of triangulation extending from Mt. 

 Lola and Round Top to San Jacinto and Cuyamaca is 

 about 500 miles in length along the axis of the scheme 



