306 THE ATLANTIC. [chap. v. 



The results of Mr. Buchanan's observations are given for 

 each section in tables forming Appendices to the several chap- 

 ters. In these tables the specific gravity is given at the tem- 

 perature at which the determination was made ; at the ten]per- 

 ature reduced to 15°*56 C. ; and at the temperature which it 

 had in the position in the ocean from which it was taken — the 

 specific gravity of distilled water at 4° C. being retained as the 

 unit. 



With a single exception, off the coast of Brazil, the densest 

 water which we have met with in the ocean was found on the 

 section from Teneriffe to St. Thomas in the heart of the north- 

 east trade-wind territory, where, from the strength and dryness 

 of the wind, the amount of evaporation must be very large. 

 Round about the Canary Islands the mean specific gravity was 

 found to be 1*02730 ; to the westward it rises steadily until in 

 long. 28° W. it has reached 1-02762. Between long. 28° W. and 

 51° W. the mean specific gravity is 1*02773, the maximum be- 

 ing 1*02781. On approaching the West Indies, it rapidly falls 

 off to an average of 1*02719 in the neighborhood of St. Thom- 

 as ; and if we take into account all the observations made on 

 the western side of the Atlantic, from St. Thomas northward 

 to the edge of the cold water which separates the Gulf-stream 

 from the coast of America, we obtain the same average, 1*02719. 

 Between Bermudas and the Agores an almost perfectly uniform 

 specific gravity was observed, the mean being 1*02713, and the 

 extremes 1*02694 and 1*02727. As Madeira is approached, the 

 specific gravity rises until it reaches 1*02746 close to the island 

 itself. The mean specific gravity on the eastern side of the 

 North Atlantic, between the latitude of St. Thomas and that 

 of the Agores, is 1*02727, or slightly higher than that of the 

 water on the western side. 



After leaving the Cape Yerde Islands, the ship's course lay 

 almost parallel to the African coast, and at an average distance 

 of about 200 miles from it. Proceeding thus in a south-easterly 



