128 KEPORT OF X'OMMISSIONEK OF FLSII AND FISHERIES. 



Ill Prof. Libbey's report for 1889 the vertical water temperatuie eurvcs 

 are represented by nine profiles, and twenty-seven sectional diagrams 

 have been ])repar('(l for the report of 1800, as well as several plates show- 

 ing the surface isothernis from time to time. The hourly changes of air 

 and surface water temperatures for each day while the survey was in 

 l)rogress are also illustrated in the same graphic manner, being based 

 upon the records made at the three stations and on board the vessels. 

 Prof. Libbey has likewise summarized the results of observations upon 

 the direction and force of the winds, as given on the ITydrographic 

 Office pilot charts of the North Atlantic Ocean, in order to aftbrd an 

 insight, if possible, into the relations between the winds and the posi- 

 tions taken by the northern boundary of the w^arm waiters coming from 

 the Gulf Stream. 



By means of the observations so far made it has been possible to 

 indicate very clearly, for the region and periods covered by the exami- 

 nation, the distribution of the bauds of equal water temperature both 

 vertically and superficially, and the relations of the cold and warm 

 water bodies to one another. The charts of surface isotherms are 

 especially interesting as furnishing a possible key, in connection with 

 meteorological conditions, to the physical changes at greater or less 

 depths, which relate to the movements of fishes. 



Aside from the more general subdivision into Gulf Stream and Lab- 

 rador (current. Prof. Libbej^ states that two different sets of currents 

 have to be dealt with in the study of this region. First are the deep 

 currents which flow in two, and generally opposite, directions alongside 

 of one nnother, their courses being controlled more by the mechanical 

 influence of the impact of one current upon the other, their relative 

 velocities, etc., than by changes in temperature and density. Second 

 come the surface currents, which flow in the same general directions as 

 the deep ones and are, of course, subject to the same mechanical laws, 

 but their courses are additionally affected to a. considerable degree by 

 the fri(;tional influence of the winds. IMoreover, they present a pecu- 

 liarity not detected in connection with the deep currents, in that cer- 

 tain branches are apparently reversed. The outlying bands of warmer 

 and denser water, which i)ass off from the shore side of the Gulf Stream, 

 seem to be drifted toward the shore or aw^ay from it to an extent de- 

 liendent upon the direction, velocity, and duration of the winds. When 

 they are forced toward the shore, thus bridging over the colder cur- 

 rents, as they proceed farther and farther from the origiiuil source of 

 their velocity, they become overpowered. Altliough retaining tuucIi of 

 their temperature and density, even to a considerable depth, their 

 direction is tlien sometimes at right angles and Anally opposite to their 

 first course. 



In connection with this investigation, the. surface-towing nets were 

 constantly employed, and a large and valuable collection of pelagic 



