32 0« the Depth and Saltness of the Ocean. 



a great degree the transmission of the rays of light or their 

 absorption. In water at the temperature of 78 to 80°, the 

 white object described was discernible at a depth of 180 feet, 

 while, in water at 36", it was lost sight of at 40 feet. The 

 object gradually diminished until it disappeared. Trials were 

 made frequently, and at every hour in the day, from early in 

 the morning till late in the evening, the altitude of the sun 

 being measured at each trial. These experiments took place 

 when the sea was nearly calm, and quite smooth ; the gi'eat- 

 est depth at which the object could be perceived was 30 fa- 

 thoms, or 180 feet. 



The next phenomenon connected with the depth of the 

 ocean, is submarine currents. They exist in various parts of 

 the ocean, where they have been traced, and are indicated by 

 their low temperature. Their actual limits, as to depth, 

 have not as yet been determined ; but they are found to pre- 

 vail at from 500 to 600 feet below the surface. They are so 

 immediately connected with the dynamics of the ocean, that 

 the investigation into their direction and causes has long 

 obtained attention. 



The saltness and specific gravity of the sea have been fre- 

 quent subjects of inquiry. The results of the Expedition will 

 throw much light upon this subject. The specimens of sea- 

 water obtained in different latitudes were, on the return of 

 the Expedition, placed in the hands of one of our most distin- 

 guished associates, Dr C. T. Jackson, of Boston, whose ability 

 as a chemist is well known to the country. He has analysed 

 them, and as it will yet be some time before the full results 

 can be published in the volumes of the Expedition, the Asso- 

 ciation will be gratified by a knowledge of his method of ana- 

 lysing, as well as by a few of the x*esults. 



Method of Analysis. — " The specific gravity of the waters 

 was taken in a small flask, with a neck of about one-fourth of 

 an inch in diametei*. A quantity of water, equal to 1000 

 grains of distilled water, was evaporated slowly to dryness 

 in a platina capsule, carrying the heat to 300° Fahr., then 

 weighed the contents by counterpoising — dissolved out the 

 muriates of lime and magnesia by absolute alcohol — filtered, 

 dried, and weighed the insoluble part. The soluble jiart was 



