398 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS 5IETE0R0L0GY. 



the sixteen points of the compass, i. e. for N., N.N.E., N E., 

 E.N.E , and so on, omitting the &?/-points, he will have before 

 him a picture of the " Investigating Chart " out of which the 

 "Pilot Charts" are constructed. In this case the alternate 

 points of the compass only are used, because, when sailing free, 

 the direction of the wind is seldom given for such points as N. 

 hy £., W. by S., etc. Moreover, any attempt, for the present, at 

 greater nicety w^ould be over-refinement, for navigators do not 

 always make allowance for the aberration of the wind ; in 

 other words, they do not allow for the apparent change in the 

 direction of the wnnd caused by the rate at which the vessel may 

 be moving^ throusfh the water, and the ansfle which her course 

 makes with the true direction of the wind. Bearing this expla- 

 nation in mind, the intelligent navigator w411 have no difficulty 

 in understanding the wind diagram (Plate V.), and in i'orming a 

 correct opinion as to the degree of credit due to the fidelity with 

 which the prevailing winds of the year are represented on 

 Plate YIII. As the compiler wades through log-book after log- 

 book, and scores do\vn in column after column, and upon line 

 after line, mark upon mark, he at last finds that, under the 

 month and from the course upon which he is about to make an 

 entry, he has already made four marks or scores, thus (////). 

 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 tallies " 

 are exhibited on Plate V. Now, with this explanation, it will be 

 seen that in the district marked A (Plate Y.) 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 enahle me to record the calms and the prevailing direction of 

 the winds for eight hours, 2144 times : of these, 285 were for the 

 month of September ; and of these 285 observations for Septem- 

 ber, the wind is reported as prevailing 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; ESE., 1; S.E., 4; S S K, 2; S., 25 

 S.S.W., 45; S.W., 93; W.S.W., 24; W., 47; W.N.W., ]7 

 N.W., 15 ; N.N.W., 1 ; Calms (the little O^s), 5 ; total 285 for 

 the 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, 



