120 MOTIONS AND PKEbSUEE OF THE ATMOSPHERE. 



strictly, but must make some allowance for translation and for change of 

 direction. * 



" The method adopted for testing the winds on each day will be under- 

 stood by reference to the adjoining plate, which is reduced from the given 

 map for January 16th, 1868, showing the barometrical readings and the 

 wind at the various stations at 8 a.m., with the gradients and their changes 

 during the preceding twenty-four hours. 



" It will be seen fcom these that the area has been, so to speak, trian- 

 gulated, as well as the situations of the reporting stations will allow. By 

 this means we have got a large number of lines of variable lengths, running 

 in different directions. Perpendiculars are let fall on each of these lines, 

 and the direction of the lines are taken according to the approximate 

 compass bearings of these perpendiculars, which are the wind directions 

 indicated, according to the Law, by differences of barometrical readings at 

 the extremities of t'he respective lines. 



" In order to render the results obtained from lines of different lengths 

 strictly comparable with each other, they have been reduced to one uniform 

 standard of 100 miles. The actual length of each Hne, and the factor 

 requisite to reduce its indications to those of the uniform standard length, 

 and also the directions for the two winds indicated according as the baro- 

 metrical reading at one end of the line is higher or lower than at the other, 

 are here subjoined. These directions, of course, differ by 180^. 



Bearing of 

 Perpendicular. 



Line. 



W. 30° N. 

 W. 40° N. 

 N. 30° W. 

 E. 10° N. 



e! 40° N. 

 N. 30° W. 

 W. 40° S. 

 W. 40° S. 

 N. 30° E. 

 S. 10° E. 

 N. 10° E. 

 N. 30° W. 

 N. 30° W. 

 W. 30° N. 

 W. 30° N. 

 W. 10° S. 

 W. 10° S. 

 W. 10° S. 

 N. 20° W. 

 N. 45° E. 

 W. 20° S. 

 N. 45° E. 

 N. 45° E. 

 N. 10° E. 

 N. 20° W. 



Valencia to Greencastle .. 



Greencastle — Nairn 



Greencastle — Leith 



Leith — Nairn 



Liverpool — Leith 



Liverpool — Greencastle .. 

 Liverpool — Scarborough . . 



Scarborough — Leith 



Helder^Nairn 



Heligoland — Nairn 



Heligoland — Liverpool 



Helder — Liverpool 



Heligoland — London 



Helder — London 



Heligoland — Rochefort ., 



Helder — Rochefort 



Weymouth — Liverpool 



Rochefort — Weymouth . , 



London — Scarborough 



Penaance — London , 



Rochefort — Brest , 



Brest — Penzance 



Brest — Valencia , 



Penzance — Roche's Point 

 Valencia — Roche's Point.. 

 Valencia — Liverpool 



Length in 

 Miles. 



Factor. 



236 

 180 

 144 

 100 

 156 

 189 

 110 

 131 

 394 

 445 

 380 

 284 

 330 

 200 

 600 

 480 

 172 

 287 

 175 

 220 

 200 

 101 

 307 

 138 

 82 

 287 





8 



1 



J. 



6 

 3 



7 



4 

 1 



i 



7 

 4 



Indicated Wind. 



E.S.E. or 



S.E. „ 



S.S.E. „ 



E. „ 



E. „ 



N.E. „ 



S.S.E. „ 



N.E. „ 



N.E. „ 



N.N.E. „ 



N. „ 



N. „ 



S.S.E. „ 



S.S.E. „ 



E.S.E. „ 



E.S.E. „ 



E. ,, 



E. „ 



E. „ 



S.S.E. „ 



N.E. „ 



E.N.E. „ 



N.E. „ 



N.E. „ 



N. „ 



S.S.E. .. 



W.N.W. 



N.W. 



N.N.W. 



W. 



w. 



S.W. 



N.N.W 



S.W. 



S.W. 



S.S.W. 



S. 



S. 



N.N.W. 



N.N.W. 



W.N.W. 



W.N.W. 



W. 



W. 



W. 



N.N.W. 



S.W. 



W.S.W. 



S.W. 



S.W. 



s. 



N.N.W. 



" These factors are, as will be seen, merely the nearest simple fractions 

 to the proportion-s between the length of each line and the standard length. 



