BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 81 



sity than this. But the water of the eastern basin was appreciably 

 denser at all depths than that of the western, corresponding densities 

 being about ten fathoms deeper in the latter than in the former. And 

 corresponding densities were found twenty to thirty fathoms higher 

 over German Bank than over Jeffrey's Bank. The profile shows also 

 in a graphic way how much more rapid the downward increase was 

 over the basins than over the banks, and consequently how much more 

 stable, vertically, their waters must have been. At the western end 

 of the profile there was again an increase in density as compared with 

 the western half of the basin, a phenomenon consequent on the up- 

 welling of cold, salt bottom water in this region, while at Stations 2 

 and 7 density near the surface was very low, corresponding to low 

 surface salinity. In the trough between Jeffrey's Ledge and the coast 

 the density agreed closely with that of the western basin, except that 

 it was rather higher on the surface, corresponding to the low surface 

 temperatures of this region. And passing northeastward along the 

 coast we find the vertical range progressively less and less, until in 

 the Grand Manan Channel the difference between surface and bottom 

 was only .6 at 45 fathoms. The information our cruise afforded as 

 to densitv is insufficient even for the northern half of the Gulf, but so 

 far as it goes, it shows that two distinct water masses can be distin- 

 guished, a light over the western, a heavy over the eastern basin, 

 partially separated by the disturbed conditions caused over Jeffrey's 

 Bank by the influx of fresh water from the Penobscot. 



Color. 



The color of the sea is of minor importance in oceanography: but 

 it can not be neglected, because it helps to form the physical complex, 

 in which the plankton finds its biological environment. The color, 

 described by percentages of yellow as indicated by the Forel scale, 

 is given in the table (p. 82). At the off-shore stations it varied from 

 27% (Station 43) to 14% (Stations 7 and 23), usually being 20%: 

 in Massachusetts Bay it was 20% at all stations at which a record was 

 made (Stations 2, 4, 6, 44, 45). West of Jeffrey's Ledge the color was 

 14% at Station 9; but grew greener as we went north, being 20% at 

 Station 11, 27% at Stations 13 and 14. Off the mouth of Casco Bay 

 it was 27%, inside the Bay 27% and 35%. Over the northeastern 

 part of the Gulf as a whole, the color was 20% yellow, except close to 

 the shore (Stations 33, 37) where it was 35%. This distribution of 

 waters of different colors does not correspond either to temperature 



