262 Mr. W. Brown on the Oscillations of the Barometer. 



north-east, — a change from south-west to south-east in this 

 case, in the southern localities, being almost impossible whilst 

 the wind continues to blow on the south-east side of the 

 locality which the storm has left. Now it is matter of general 

 observation that the wind very seldom changes in this direc- 

 tion, or from south-west to south-east, being indeed termed 

 by nautical men " backing" ; there is however a particular 

 case in which the wind sometimes changes from S.W. to 

 S.S.E. in the northern or central portions of a space occupied 

 by a storm ; and that is in the occurrence of a storm as that 

 of § 16, the circumstances of which fully explain the excep- 

 tion, for the change is the consequence of the collision of the 

 currents by which the S.S.E. wind is produced, and hence it 

 takes place at what for the moment is on the northern verge 

 of the south wind, where of course a change produced by a 

 north-east wind meeting it may make it south-east*. 



Having carried out thus far the results of the principles 

 stated at the beginning of this paper, I may now proceed to 

 give the observations which I have collected, and first those of 

 the wind, extracted from the Shipping Gazette. 

 Scotland. — Orkney, Longhope. — " November 1. N., moderate. 2. 



S.E., fresh breeze. 5. N.W., moderate. 8. S.W., blowing hard; 



rain. 11. E., strong breeze; rain. 13. N.E., squally. 15. 



N.N.E., fresh. 16. N.E., frosty. 19. E., strong breeze; rain. 



20, 21. N. to N.E., frost and sudden squalls. 22. E. to S.E. 



23. E., fresh breeze." 

 Pentland Frith. — "Nov. 7. N.W., moderate : night, S.W. ; very 



strong throughout the night. 8. S.W. 18. W., moderate. 19. 



S.E., moderate ; rain : 6 p.m., N.E., moderate." 

 Thurzo.—" Nov. 2. S.E., moderate. 8. S.W., fresh breeze. 10. 



N.W., heavy gale. 11. N.E. 17. S.W. 18. N.E. 19. S.E., 



moderate weather. 23. S.E." 

 Peterhead.—" Nov. 1. N.W., light. 3. S.E. to E.S.E., light breezes. 



4. E., moderate. 5. N.E., fresh breeze. 8. S.W., fresh breeze. 



9. S.W., strong gale. 19. S.E. to N.E., rainy. 20. N.E., 



strong breeze. 23. E.N.E., fresh breeze. 24. E., strong." 

 Inverness. — "Nov. 19. N.E., calm and raining. 26. N.E., calm; 



rain." 

 Aberdeen.— " Nov. 17. E.N.E. 18. Variable, E.N.E." 

 Mull — Tobermorey. — "Nov. 3. S.E. 4. S.E., moderate breeze. 5. S.E. 



to E., light breeze. 7. Variable ; light airs and heavy showers of 



rain. 8. S-W., strong gales. 9. S.W., "fresh breeze, with rain 



at intervals. 10. E.N.E., fresh breeze. 11. E., strong breeze. 



12. W. to S., light airs; variable. 13. E.N.E., fresh breeze. 



* In these paragraphs I have omitted any mention of the differences of 

 the mean pressure on different latitudes of the surface of the earth, not 

 because of its unimportance, but because it would merely be a transcript 

 of my essay on that subject in this Magazine, vol. xx. p. 469. 



