598 Mr. J. Y. Buchanan on Chemical Work 



water which separates the Gulf-stream from the coast of America, we 

 obtain the same average, 1-02719. Between Bermuda and the Azores an 

 almost perfectly uuiform specific gravity was observed, the mean being 

 1-02713, and the extremes 1-02694 and 1-02727. As Madeira is ap- 

 proached 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's and that of the Azores, is ' 

 1-02727, or slightly higher than that of the water on the western side. 



After leaving the Cape-Verd 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 direction, the specific 

 gravity fell rapidly from 1-02692 off St. Iago on the 10th August, to 

 1-02632 on the 12th, after which it retained the low mean specific 

 gravity of 1-02627 until the 21st August, when the course was changed 

 to a westerly one along the equator. The specific gravity of the 

 water on this day was the lowest hitherto registered for a surface-water ; 

 it was 1-02601, in lat. 3° 8' N., and on the boundary line between the 

 equatorial and Guinea currents. The same low specific gravity was 

 observed in following the equatorial current as far as St. Paul's rocks, 

 after which it quickly rose as the Brazilian coast was approached ; and 

 the maximum of 1*02786 was obtained on the 26th September, when 

 off the entrance to Bahia, in latitude 13° 4' S. 



The observations in the South Atlantic were limited to a line down 

 the western side as far as the Abrolhos Bank, and thence across to the 

 Cape of Good Hope. In the region of the south-east trade-wind, there- 

 fore, we have only a few observations close to the coast ; and as we have 

 seen in the North Atlantic, on the voyage from Teneriffe to St. Thomas's, 

 the specific gravity is higher in mid-ocean than either on the east or 

 the west side, so in the South Atlantic it is possible that the same may 

 hold good. Prom the Abrolhos Bank to Tristan d'Acunha the specific 

 gravity sinks steadily from 1*02785 to 1*02606, and from Tristan to the 

 Cape of Good Hope, along a course lying between the 35th and the 

 37th parallels of south latitude, the mean specific gravity was 1*02624. 

 Between the same parallels of north latitude the mean specific gravity 

 was 1*02713. 



It must be remembered that the results obtained can only be held 

 good for the season of the year in which they were observed, and that 

 the observations in different latitudes were made in different seasons, 

 and, further, that all the observations north of the line as far as 20° N. 

 were obtained on the eastern side, and those to the southward of it 

 as far as 30° S. were obtained on the western side of the ocean • so 

 that it would be unwise to attempt to draw any general conclusions 

 from such imperfect data. Considering, however, our four parallel 

 sections, we have at least this positive result — that in the month of 

 June and mean latitude 36° N. the surface-water in mid-ocean has a 



