208 OBSERVATIONS ON THE WINDS. 



tion. As there certainly is a doubt as to the accuracy of the recorded 

 direction of the wind to the extent of two points — to lay down rules for 

 sailing over any area with a course limited to a few degrees, certainly 

 appears to be a needless refinement with the present data to argue upon, 

 but in future years extended knowledge may make it possible to lay down 

 such rules. 



(143.) In comparing the observations, recorded by Mr. Osier's self- 

 registering wind-guage at Liverpool, as shown in page 204, with the second 

 diagram adjoining page 171 — that for lat. 52° N., and long. 15° W. — or off 

 the West Coast of Ireland, where we might expect to find some degree of 

 similarity, there appears to be scarcely any accordance at first sight. But 

 upon referring to the evidence of the greater force of the Westerly winds 

 over the Easterly, as shown by the figures (136), page 204, we arrive at a 

 reason why this apparent discrepancy exists. If the arrows on the West 

 (or windward) side of these diagrams were enlarged in proportion to the 

 relative force, and the Easterly arrows diminished in like manner, there 

 would be a much nearer approximation. This comparison will demon- 

 strate how the direction of the valley of the Mersey, and the line of docks 

 and walls at Liverpool around the observatory, diverted the true direction 

 of the winds. For the purpose of still further exemplifying this, the mean 

 of the observations recorded at Birmingham for four years, by another 

 anemometer of Mr. Osier's, is given. Although this is inland, and neces- 

 sarily subject to land influences, the Westerly preponderance is clearly 

 marked, and serves to bear out the modern discovery of the progress of 

 Cyclonic disturbances across the British Isles from West to East, their 

 centres generally passing North of our islands. 



The diagrams, as we give them, or the figures in Maury's chart, must be 

 studied, should any greater exactness in the relative duration of any wind 

 be required than can be acquired at a cursory glance ; and in the former 

 case, as was before explained, the length of the arrow apphed to the scale 

 at the bottom of the plate will give the exact ratio per cent, of the wind 

 represented by that arrow. 



One general remark only need be given ; it is, that the greatest irregu- 

 larity in the direction of the wind in these latitudes appears to occur about 

 the Azores; during the summer months the wind is frequently from Northern 

 quarters, driving before it the colder water from the polar regions, and thus 

 abnormally reducing the temperature. Besides this, there appears to be 

 a conflict between this Southern and Western tendency, and the Trade 

 Wind which is estabhshed to the West of them. 



(144.) Bay of Biscay. — The winds in the Northern part of the Bay of 

 Biscay do not differ greatly from those experienced in the entrance of the 

 English Channel. As we approach the head of the bight, however, it is 

 necessary to use great caution, and observe all indications of the change 

 of the wind. 



The prevailing winds in the Bay of Biscay are those from N.W., West, 

 and S.W., with frequent severe gales from those quarters, accompanied by 

 rain, hail, and thick weather, and a mountainous sea. A low barometer, 

 a Westerly swell, and other threatening appearances, indicate the approacn 

 of one of these gales. Very often it commences at South or S.W., with 



