46' SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. JO 



we have given an isoplethic diagram drawn from the mean tempera- 

 tures for each month at each of his stations. It is to be noticed here 

 that in the months January to July the observations along the south- 

 ern steamer route, that is to say, the winter course between the 

 English Channel and New York, are given, and that is the same 

 course for which the most of our observations are found. From 

 August to December they follow the northern route, that is to say, 

 the summer route, which is considerably farther north, particularly 

 in the middle part of the ocean, where the difference for example at 

 40° west longitude amounts to 4° in latitude and at 46° west longi- 

 tude, 5° in latitude. This explains the break in the values which 

 occurs between July and August and also between December and 

 January. 



We see that in the months January to July the minimum is at 

 station No. 9. at 51° west longitude and 41° north latitude, while 

 from August to December it falls at station 8, eastward of this at 

 about 46° west longitude and 46° north latitude. The explanation 

 is easily apparent, for station 9 is upon the southern route immedi- 

 ately on the west side of the earlier mentioned " cold wedge " due to 

 the Labrador current. Since this region of cold Labrador water 

 follows the eastern declivity of the Newfoundland Bank from north- 

 east toward southwest, it is plain that if we go further north to 

 the northern steamer route, the region of minimum temperature 

 must be found further eastward near station No. 8. 



On the whole, this isopleth diagram gives a good representation 

 of the principal features of the distribution and change of tempera- 

 ture for the year in this entire oceanic region. 



Dr. H. Liepe in his paper entitled " Temperature Variations of 

 the Surface of the Ocean from Ouessant to St. Pauls Rock " (1911) 

 has investigated the variations of eight stations during the 20-year 

 period from 1884 to 1903. These were 1° fields which he chose in 

 the most frequented shipping routes along the east side of the Atlan- 

 tic Ocean, from the English Channel and southwards towards St. 

 Paul near the equator (see pi. 15, LVIII). In the same manner as 

 Petersen, Liepe assembled for each month all observations of the 

 surface temperatures within 1° fields as given by the ships' log-books 

 of the Deutschen Seewarte. The number of the observations within 

 the different fields varied a great deal. On the average there were 

 about 17 observations a month for each of the eight 1° fields, and 

 the highest number of observations for one field during a month 

 reached 46. An under limit of five observations per month was 

 fixed. 



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