76 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'JO 



between these two stations and our fields is, however, very great, 

 and from the station 7 it is over 3,100 kilometers to our most 

 southerly fields, or about as much as from the Channel to New- 

 foundland (see pi. 15, fields VII, VIII, 3-5, 7-14; see also fig. 56). 



It is of great interest to compare the results with the observa- 

 tions in the 10° square fields between 5° and 15° north latitude 

 and 25° and 35° west longitude, shown in plate 15, field 20 as given 

 for the years 1900-1913 in the Dutch " Monthly Meteorological 

 Data for 10° Squares in the Atlantic and Indian Oceans " (Konink- 

 lijk Niederlandsch Meteorologisch Instituut, No. 107-a Utrecht 

 1914). In general the fields of 10° square are too large to show 

 the true conditions by merely taking mean values of all observa- 

 tions within these fields without reference to their local situation. 

 Moreover the observational material itself within these great fields 

 is in most of the fields too meagre to give satisfactory values. In 

 the 10° square field which we have referred to the number of 

 observations in most months is about 10 per month but varying 

 between 5 and 30, sometimes more. We must on this account 

 look for some irregularities in the mean values for the different 

 months. We have computed the mean yearly temperatures for 

 this field, both for the calendar year January to December and 

 for the twelve months September to August. The values obtained 

 are graphically given in the topmost curve of figure 39. The heavy 

 full drawn line is the yearly curve for September to August and 

 the heavy dotted line, the curve for the calendar year. We have 

 also given the curves of the February temperature (weak full drawn 

 lines) as well as of the March temperature (weak dotted lines) 

 for the same field. Under these curves we have drawn the curves 

 B and A. These relate to our two most southerly fields of cor- 

 responding longitudes between 20° and 30° west longitude, which 

 are about 2500 kilometers further north (see pi. 15, fields 13 and 

 14). The curves are for February. One must admit that between 

 these curves and the February and March curves for the tropical 

 field there exist with certain exceptions a very great similarity. 

 It is apparent that the variations in the tropical fields are much 

 greater than in our fields further north. 



The two yearly curves for the tropical field have a characteristic 

 form similar to our February and March curves particularly for 

 10° longitude field between 20° and 40° west longitude (see fig. 

 30). This similarity would be yet more striking if we should com- 

 pare the tropical yearly curve with our smoothed curves of figures 



