IO2 On Similarities in the 



meter. Thus, in the region of general easterly current, the 

 specific gravity (at 60 F.) of the surface ranged between 1-0255 

 and 1-0258, but where the current was strongest it fell to 

 1-0249 m l at - 9 2 $'' an d 1-02475 in lat. 7 26' N. It rose 

 rapidly immediately the westerly running water was reached, 

 being 1-02621 in lat. 2 34' N. 



The diagram shows also in a very marked way the protective 

 action of the fresh surface water in preventing the penetration 

 of heat into the lower layers of the water. A temperature 

 of 60 F. is found here (lat. 9 10' N.) at a depth of 50 fathoms 

 from the surface, while in the westerly running current, a little 

 further south (lat. 2 34' N.), the same temperature occurs at 

 a depth of over 100 fathoms. The effect is even more striking 

 if the mean temperature of corresponding layers is compared 

 as in the table, p. 103. Besides stations 267 and 270, the 

 figures for station 278, in lat. 17 12' S., with the island of Tahiti 

 in sight are given. No current was logged here, but the effect 

 of high surface salinity, gradually falling as the depth increases, 

 in propagating heat downwards, is made particularly evident. 



If the figures in the tables (p. 103) be studied it will be seen 

 that the temperature follows the density, that is, the further the 

 high density penetrates the deeper do we find a high tempera- 

 ture. At station 278 the high surface density is found to 

 persist almost undiminished down to 100 fathoms, while 

 at No. 270 it does not persist much beyond 25 fathoms, 

 Accordingly, at 278 we find a mean temperature between 

 80 and 150 fathoms, 10-3 higher than at 270. From the 

 surface to 80 fathoms there is very little difference in the 

 amount of heat in the water. Besides a greater range of 

 salinity in the water of different layers at station 278 than at 

 station 270, there is certain to be a greater annual range of 

 surface temperature at lat. 17 S. than at lat. 2 N., and this 

 will also be helpful in propagating heat downwards. Further, 

 at the equatorial station the concentrated surface water is 

 being hurried away westwards at a rate of 70 miles in 24 hours, 

 while at lat. 17 S. it was not found to have any very apparent 

 motion. At station No. 267 there is a layer of very low salinity, 

 of probably not more than 20 fathoms in thickness, yet this 



