Reviews — Pourtales on the bed of the Gulf-stream. 425 



II. — The bottom of the Gulf-steeam and Atlantic Ocean 



NEAR THE CoAST OF NORTH AMERICA. Bt L. F. PoURTALES.^ 



POURTALES first tells us of the great share which the G-overn- 

 ment of the United States took in the exploration of the deep 

 sea through the Coast Surveys, which first (1844:) were under the 

 superintendence of the late Professor A. D. Bache, and during the 

 last three years under the direction of Prof. B. Peirce, who gave 

 permission to the above publication. Pourtales first describes two 

 important instruments, which are used for deep-sea explorations, 

 namely, the sounding cups of Lieutenants Stellwagen and Sands. 

 Each sounding is carefully put away in bottles, which bear the date, 

 the longitude, latitude, and the depth in fathoms. The number of 

 such samples is already 9,000. The undertaking, which has not 

 nearly concluded its task, was confined only to the Atlantic Coast of 

 North America, between Cuba and Cape Cod in Massachusetts, that 

 is to say, between the 20th and 40th degrees of latitude, 



Pourtales distinguishes principally two kinds of deposits in this 

 part of the ocean, namely, a siliceous deposit and a lime deposit. 

 The first runs along the coast from Cape Lad to Cape Florida, the 

 latter as Coral lime occurs on the Coast of Cuba and ofi" the Bahama 

 banks, as well as to the South of Florida, and as Polythalamia lime 

 in greater dejDths. 



It is remarkable that the siliceous deposits begin with the cold 

 northern current, whilst the lime deposits are confined to the warm 

 southern current. It is probable, however, that the organic life which 

 produced this lime deposit depends more on the depths, than on the 

 temperature, which continues constant in greater depth, and is inde- 

 pendent of the temperature at the surface of the sea. 



Somewhat east of Long Island we find a muddy sea-bottom ; this 

 mud originated apparently from the former extension of the Tertiary 

 deposits, whose remains now form only a few g\\^% at scattered 

 localities along the Coast of Massachusetts. The siliceous deposit 

 reaches as far down as 100 fathoms, and slopes gradually towards 

 the deeper parts of the ocean. It consists of yellow sand, and in 

 the Gulf of Mexico of pure white quartz, mixed with a few grains 

 of hornblende and felspar, but seldom of pebbles of old sedimentary 

 rocks. Near the Bay of New York this sand is much mixed with 

 glauconite and casts of Polythalamice from the greensand of New 

 Jersey. They are easily seen with an ordinary magnifying glass. 

 The region nearest the' coast, of a depth of from 10 to 12 fathoms, 

 affords only very few and small Polystomella, owing to the constant 

 movement of the water. The next zone contains several species of 

 Miliolidce, but seldom at a depth of more than 40 fathoms. 

 Beyond this zone they are found, but very rarely. Truncatulina 

 advena, d'Orb., is not rare in depths of from 25 to 70 fathoms. In 

 this region begins the fourth zone, which reaches down to 100 

 fathoms, and affords the larger types of the MarginuUnce and 



1 Petermann's Mittheilungen, vol. xvi., 1870, xi. 



