20 



MEM(JIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



The following table shows the leading particulars respecting those storms whose course was 

 for some days towards the west: 



Table IV. — American .storms advancing westerly. 



Column 1 shows the number of reference ; column 2 shows the dates of beginning and end of 

 the observed movement as long as the course continued westerly ; column 3 shows the latitude at 

 the beginning and end of tliis portion of the path ; polnnni 4 show.s the longitude at the beginning 

 and end of this portion of the path; column 5 shows the prevalent direction of the path while 

 moving westerly ; column 6 shows the average velocity of progress of the storm center (in miles 

 per hour) wliile the course continued westerly ; column 7 gives a brief indication of the subsequent 

 course of each storm. On Plate XH, Fig. 1, tliese tracks are delineated, and are designated by 

 the same numbers as in the table. 



31. The general results of this table correspond very closely with those deduced from Table 

 III. The lowest latitude of any storm center shown in this table is lO^.C N. The lowest latitude 

 shown in Table III is 10o.3 N. The average velocity of these storms while moving westerly was 

 11.9 English statute miles per hour; the average velocity of the storms mentioned in Table III 

 while moving westerly was 17.4 miles per hour, lu nine of these cases the course of the storm 

 became due north before reaching the parallel of 30°, and tlie average direction of these storms in 

 the early part of their course was west 20^.5 uorth. 



Storm No. IS api)areutly advanced directly west, and storms Nos. 9 and 16 apparently moved 

 for a day or two a little south of west. Table III shows thiity one cases in which the course of storms 

 was towards the uorth of west, and only two cases in which the course was south of west, viz, one case 

 in which the course was two degrees south of west, and the other eleven degrees south of west. 

 From the two tables we perceive that the ca.ses in wliii'h tropical storms move in a direction north 

 of west are fifteen times as frequent as the cases in which they move in a direction south of west, 

 and in none of the cases here reported was the southerly motion very decided. 



32. In order to determine whether during the period here considered there may not possibly 

 have been other storms which moved in a direction corresponding moi'e nearly with that of the 

 northeast trade winds. I have made a careful comparison of the international observations. 

 Five sixths of ail the storms enumerated in Table TV occurretl in the months of August, September, 

 and October. 1 therefore selected these three months for special comparison. For the years 

 lS76-'77-'78 and '79 the barometric curves were drawn for these months for all the stations reported 

 in the International Bulletin, between the equator and latitude 26° N. 



