342 CALIFORNIA ACADEMY OF SCIENCES. 



Arena, one between Point Carmel and Point Sal, and one 

 stretching from the Santa Barbara channel towards San 

 Diego. The bottom of the one hundred fathom plateau 

 has an average temperature of 45°. 



(5.) Fifty miles off shore the average depth of the ocean 

 is 1000 fathoms. At this distance the existence of a sub- 

 marine mountainous grade, which is highest in latitude of 

 Point Carmel, alters the isothermal lines of the ocean. The 

 same action on the temperature of the water is repeated, 

 though in a less degree, by another submarine grade tend- 

 ing southward towards San Diego. 



(6.) The result is, that the isothermal line of 40°, com- 

 mencing at Trinidad Head at a depth of about 350 fathoms, 

 and which is found to be off San Diego 500 fathoms deep, 

 sinks off San Francisco to 700 fathoms depth, and. off Point 

 Sur still deeper. Therefore, off San Francisco and off Point 

 Sur a greater volume of warm water is found in ^)roportion 

 than at any other point on the coast. 



(7.) For the same reason the isothermal lines between 

 the two named points are bent upward, indicating thereby 

 that the direction of the current is generally southward, and 

 that the cold waters are crowded back and upwards by the 

 submarine mountain. 



(8.) All the isothermal lines, 50 miles off shore, show 

 generally a constant increase of temperature towards San 

 Diego; still the isothermal line of 40° is only 100 fathoms 

 deeper at San Diego than at Trinidad Head. 



(9.) One hundred miles off shore the same regularity is 

 observed. On the line of San Francisco, however, the high 

 surface temperature of 58.2° is cooled 18° inside of 300 

 fathoms depth, and off'Point Carmel and Point Sal, a similar 

 proportion is observed; while off San Diego a depth of 600 

 fathoms is reached before the temperature is lowered to 

 this extent. 



(10.) Two hundred and twenty miles distant from shore 

 the evenness of the isothermal lines is remarkable, indica- 



