92 bulletin: museum of comparative zoology, 



is similarl}' explained bj^ the indraught into the eddy of the compara- 

 tively fresh water off Cape Ann. Off Cape Cod (Station 43) the water 

 was considerably salter than off Cape Ann, the mean for the upper 

 fifty fathoms being about 32.7, instead of 32.4 as it was at Stations 

 2 and 7; i. e., in this region the influence of the coast water was felt 

 but Httle. 



Unfortunatelv we vet hsLve so little data for the salinities of the 

 region south of a line from Cape Ann to Cape Sable, that an attempt 

 to extend the chart of circulation over the southern half of the Gulf 

 would be little better than guess work. 



Comparison w'ith previous records of tejiperature and salinity. 



In July and August, 1873, Verrill found nearly the same surface tem- 

 pera tm'C fifteen to twenty miles southeast of Cape Elizabeth as we did 

 last summer, 62°-6o°. Near Seguin Island, August 20, he records 59°; 

 this is very close to our Station 40, where on August 22 our reading was 

 58°. But by September, 1873, the surface temperature had fallen 

 several degrees below our August records, the surface temperature east 

 of Jeffrey's Ledge, and generally over the western basin opposite Cape 

 Arm being given by Verrill as 57°-58°, i. e., autumn cooling had proba- 

 bly set in by that time. And his records near ■Slonhegan and Matini- 

 cus Rock are from 2°-3° lower than ours a month earlier. But in 

 Massachusetts Bay his records are 59°-64°, suggesting that seasonal 

 cooling in that region was more rapid in 1912 than in 1873. 



The temperature data obtained by the U. S. Coast Survey in 1874 

 is of slight value, because the surface readings are not reliable (\ errill, 

 1875, p. 413, footnote) ; and there is no way of estimating the probable 

 error, which may be several degrees. But so far as they go they sug- 

 gest that the surface of the Gulf was several degrees warmer in that 

 year than in 1912, with surface temperatures of 60-69° in its south- 

 western part. On Cashe's Ledge, and on the northern part of Jeffrey's 

 Ledge readings of 55-58° were obtained, probably an index of active 

 vertical tidal circulation. 



Dickson's (1901) charts for July and August, 1896, and July and 

 August, 1897, show a very different distribution of surface tempera- 

 tures in the Gulf from what we encountered: for they do not show 

 the cold coast-band east and north of Cape Ann, while in July, 1897, 

 the surface temperature of the whole of the Gulf east of about 69° 

 W. Long, is given as below 59°; the smaller area west of 69° Long., 60° 



