2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



p. 229) and partly by the lateral oscillation in summer and winter 

 (compare 1909, p. 227). 



It was therefore to be expected that during- the colder parts of 

 the winter and towards the end of it the surface temperature could 

 be used as an indicator of the heat condition of the ocean masses 

 to relatively great depths. Accordingly one would expect that the 

 yearly variations of the surface temperature of the sea during the 

 coldest part of the winter would correspond to the variations of 

 the winter temperature of the water layers lying underneath. If 

 that is in fact so, a study of the surface temperature of the sea 

 during the winter should give valuable hints on the variations of the 

 temperature of the water-masses which are carried along by the 

 various ocean currents. 



In our investigations of the surface temperatures of the Atlantic 

 Ocean it was natural that our attention should be drawn to the 

 very large collection of ships' log-books at the Deutschen Seewarte. 

 Our colleague, Herr Adolf H. Schroer undertook therefore the 

 task of going to Hamburg in order to make necessary abstracts 

 from these log-books. In this work he received the kind coopera- 

 tion of the direction and staff of the observatory, so that he was 

 able to attack the matter in the best way. 



In the choice of the region of the sea to be investigated the 

 observational material gave decisive indications. The choice fell 

 upon the much travelled ship course between the English Channel 

 and New York (see fig. i and pi. 15). The observations of the 

 air and surface temperatures were collected for the period of years 

 1898 to 1910 according to one degree fields. In these tables all 

 the observations which could be found were entered, principally 

 being those of steamships, but including those of sailing vessels. 



Further classification was made by arranging the observations 

 in decades. We chose first the three decades at the end of the 

 winter, from the 15th of March to the 13th of April. We found 

 well-marked yearly variations which made it desirable to investi- 

 gate whether these were more widely extended both in time and 

 in ocean situation. 



Accordingly we assembled the observations of the air and ocean 

 temperatures in the same region for the coldest season ; that is, for 

 the three decades from February 3 to March 4; and we also col- 

 lected a great number of observations of air and surface tempera- 

 tures from a more southerly region, that between Portugal and 

 the Azores. This region extended from ten degrees to forty degrees 



