392 THE DEPTHS OF THE SEA. [CHAP. vm. 



caused by a ' modified case ' of the general oceanic 

 circulation, and neither by the Gulf- stream nor by 

 the anti-trade drift. 



Although there are, up to the present time, very 

 few trustworthy observations of deep-sea tempera 

 tures, the surface temperature of the North Atlantic 

 has been investigated with considerable care. The 

 general character of the isothermal lines with their 

 singular loop-like northern deflections, has long 

 been familiar through the temperature charts of the 

 geographers already quoted, and of late years a pro 

 digious amount of data have been accumulated both 

 abroad and by our own Admiralty and Meteoro 

 logical Department. 



In 1870, Dr. Petermann, of Gotha, published 1 an 

 extremely valuable series of temperature charts, 

 embodying the results of the reduction of upwards 

 of 100,000 observations, derived chiefly from the 

 following sources : 



1. From the wind and current charts of Lieu 

 tenant Maury, embodying about 30,000 distinct 

 temperature observations. 



2. Erom 50,000 observations made by Dutch sea- 

 captains, and published by the Government of the 

 Netherlands. 



3. Erom the journal of the Cunard steamers be 

 tween Liverpool and New York, and of the steamers 

 of the Montreal Company between Glasgow and 

 Belleisle. 



4. Erom the data collected by the secretary of the 



1 Der Golf-Strom und Standpunkt der thermometrischen Kenntniss 

 des Nord-Atlantischen Oceans und Landgebietes im Jahre 1870. 

 Justus Perthe's ' Geographische Mittheilungen/ Band 16. Gotha, 1 870. 



