gi4 On Wind:'. 



\\ind partakes lefs of the northerly, than when the fori 

 IS in or approaches to the fouthern tropic, (Phil. Tranf. 

 Abrid. ii. p. 134; and Schncd. Abhandl. 1762, p. J75 :) 

 which is direAly contrary to Hadley's fyftem ; for when 

 the fun is in the fouthern tropic, the norih wind mufl: tra- 

 verfe more of that fpace in which the earth's motion ealt- 

 •ward is ftrongeft, and therefore fliould participate more of 

 that motion, as Hadiey himfelf (iates : thnuiih ftill panakiug 

 of it in a fnialler degree than that which the globe iifelf pof- 

 feffes, it (hould appear to move welhvards ; yd it fhould pro- 

 portionably retain lefs of its original direftion from north to 

 fouth than when it had iraverfed a fpace more didant from 

 the equatot-, whereas the fact is that it retains more, and 

 often paffes into the fouthern hemifphere into the 3° fouth 

 iatitude without having any calknn direction, (Marchand iii. 

 P-55^5) and an analogous fa6l is obferved with refpeft to 

 the iouth-eaft wind when the fun is in the northern tropic. 

 Hence it is evident, that it is from the approach of the fun, 

 and not from the latitude traverfed, that the eaftern direction 

 is derived; nav, the wind is often more eafterlv than north- 

 erly between latitude 23° and 28 : (Porter's Obfervations, 

 p, 126.) He even obferved that tlie trade winds extended 

 far beyond the tropics when the fun is in the fame hemi- 

 fphere, which (liows it is the fun that caufes them.- 



Eddj is a term introduced on this fubjeA, which explains 

 nothing when its caufe is not nlligned and proved; the trade 

 winds are often interrupted by the approach of land ; but the 

 interruption, as Fofter mentions, extends only to a few miles. 

 Ibid. 127. 



The nionfoons or periodical trade winds depending on local 

 circumttances, fufficiently explained by Dr. Halley, I fhall 

 here pafs over ; though certainly much may be added from 

 obfervations made by fubfequeut navigators and travellers. 

 I ftiall therefore confine myfelf to the variable winds, a lub- 

 je6l much more obfcure. 



Of Variable Winds. 



With refpe£l to winds we mud: lay down one general and 

 fundamental principle, which is, that they always originate 

 at the extremity of that point towards which they proceed. 

 Tlius the eafterly trade wind begins at the point nearell the 

 fun, which it follows, and is perpetually renovated and fup- 

 pticd from parts ftill more eallerly. Thus in the year 1709 

 a north wind was fooner perceived in England than at Dant- 

 zic (Phil. Tranf. Abrid. iv. part ii. p. 115. And Wargentin 

 notes, that when the wind changes to the weft, this change 

 takes place at Mofcow before it happens at Abo, which is 



fevtral 



