SCIENCE. 



[N. S. Vol. II. No. 30. 



TEE CA USES OF THE G ULF STREAM. 



Shortly after the first voyage of Colum- 

 bus, the existence and some of the charac- 

 teristics of the Gulf Stream became known, 

 and with Franklin's experiments as to its 

 temperature, scientific observations upon it 

 began. Since then, many other observations 

 as to its depths in places, temperature and 

 direction have been added to the sum of in- 

 formation on the subject, knowledge of 

 which, in the form of scientific reports, 

 monographs and magazine articles, has 

 more or less found its way to the public ; 

 some of the accounts, however, stopping 

 very far short of the ultimate interest in 

 the subject derivable from determination 

 of the causes of the stream. The statement 

 that the trade winds heap up the equatorial 

 waters on the eastern shore of Central 

 America, therebj' giving a ' head ' to the 

 Carribean Sea and the Gulf of Mexico, 

 seems to suffice to most persons for an all- 

 sufficient explanation of the generation and 

 behavior of the Gulf Stream. But it ought 

 to be obvious that, although winds do, as is 

 observable in small areas, heap up waters 

 against obstructive lines upon which thej' 

 impinge, the movement of the equatorial 

 waters towards the west cannot be the sole 

 cause of the Gulf Stream. On the contrary, 

 whatever head actuallj' exists there is pro- 

 duced by several agencies causing the 

 thrust of waters in the form of a mighty 

 current. 



Seeking for a single cause of the phenom- 

 ena, one will be foiled. He would make an 

 attempt at the bottom of much unproduc- 

 tiveness in research, arising from seeking in 

 nature for some one cause to account for 

 any phenomenon in its entirety. In seeking, 

 therefore, for the cause of the Gulf Stream, 

 we must resolve the idea of cause into that 

 of causes, called, if one will, primary, sec- 

 ondary, etc., but still, in the aggregate, 

 activities of many existing conditions. 

 These are the globular form of the earth ; 



its rotation on its axis ; the difference, in 

 correspondence with latitude, of its rotary 

 velocity; the difference in temperature, in- 

 volving density, between polar and equa- 

 torial waters ; the direction and force of the 

 trade winds ; the head of water produced 

 by those winds and other agencies at the 

 the Gulf Stream, and the correspondingly 

 lower level at the places whence a portion 

 of its waters are so derived ; the volume of 

 discharge contributed to the Carribean Sea 

 and the Gulf of Mexico by the rivers flow- 

 ing into them ; the increase in volume of 

 those waters through the long continued 

 heat to which they are subjected while con- 

 fined within the caldron formed by those 

 basins — -these, and nothing less, represent 

 in fact the assemblage of the causes of the 

 Gulf Stream. 



The Coast and Geodetic Survey of the 

 United States has, within the last few years, 

 made verj' valuable additions to knowledge 

 of the Gulf Stream, through the investiga- 

 tions of Lieutenant Pillsbury, of the Navy, 

 commanding the steamer Blake, but these 

 relate to details, which although interesting, 

 do not involve the largest question relating 

 to the stream in its verj- existence. Lieu- 

 tenant Pillsbury established the fact of the 

 absence of the supposed hill ranges, in and 

 parallel to the trough in which the stream 

 for a while flows in its course along the 

 shores of the United States ; the iudeter- 

 minateness of the position of its boundarj'- 

 line, constituted by Arctic water lying be- 

 tween it and the coast, well described bj' 

 the term ' cold wall,' and he also proved 

 the iudeterminateuess of the bauds of alter- 

 nating warm and cold water in the stream, 

 caused bj^ the irregular dispersion of surface 

 water by winds. The impossibility of 

 recognizing at all times by temperature the 

 position of the axis of movement of the 

 stream is thus clearlj^ shown. He dis- 

 covered fluctuations in the stream, in direc- 

 tion and strength, as dependent upon the 



