258 THE PHYSICAL GEOGRAPHY OF THE SEA. 



wind. Bearing this explanation in mind, the intelhgent navigator 

 will have no difficulty in understanding the wind diagram (Plate 

 v.), and in forming a correct opinion as to the degree of credit due 

 to the fidelity with which the prevailing winds of the year are rep- 

 resented on Plate VIII. 



As the compiler wades through log-book after log-book, and 

 scores down in column after column, and upon line after line, 

 mark after mark, he at last finds that, under the month and from 

 the course upon which he is about to make an entry, he has al- 

 ready made four marks or scores, thus (I U I). The one that he 

 has now to enter will make the fifth, and he " scores and tallies," 

 and so on until all the abstracts relating to that part of the ocean 

 upon which he is at work have been gone over, and his materials 

 exhausted. These " fives and talhes" are exhibited on Plate V. 



Now, with this explanation, it will be seen that in the district 

 marked A (Plate V.) there have been examined the logs of vessels 

 that, giving the direction of the wind for every eight hours, have 

 altogether spent days enough to enable me to record the calms 

 and the prevailing direction of the winds for eight hours, 2,144 

 times : of these, 285 were for the month of September ; and of 

 these 285 observations for September, the wind is reported as pre- 

 vaihng for as much as eight hours at a time : from N., 3 times ; 

 from N.N.E., 1 ; N.E.,2; E.N.E., 1 ; E.,0; E.S.E., 1 ; S.E.,4; 

 S.S.E., 2; S., 25; S.S.W.,45; S.W., 93 ; W.S.W., 24 ; W., 47 ; 

 W.N.W., 17; N.W., 15; N.N.W., 1 ; Calms (the little O's), 5; 

 total, 285 for this month in this district. 



The number expressed in figures denotes the whole number of 

 observations of calms and winds together that are recorded for 

 each month and district. 



In C, the wind in May sets one third of the time from west. 

 But in A, which is between the same parallels, the favorite quar- 

 ter for the same month is from S. to S.W., the wind setting one 

 third of the time from that quarter, and only 10 out of 221 times 

 from the west ; or, on the average, it blows from the west only 

 1|- day during the month of May. 



In B, notice the great " Sun Swing" of the winds in September, 

 indicating that the change from summer to winter, in that region, 

 is sudden and violent ; from winter to summer, gentle and gradual. 



In some districts of the ocean, more than a thousand observa- 



