Motions of Different Currents of Air. 



cm 



24° more northerly than the surface wind ; while there were only 58 results shewing a more southerly motion, 

 and 19 in which both currents proceeded from the same point. It might be supposed that the regular differ- 

 ence of these currents was due to some peculiar configuration of the surface of the country around the Obser- 

 vatory, but this is disproved by the results of the comparison of the upper currents with each other ; thus, the 

 cirro-stratous current, compared with the scud-current, shews on the average of 255 results that the upper 

 current proceeds from a point 14° more northerly than the lower current : a similar result is obtained from a 

 comparison of the cirrous current with the scud-current. 



Table 97. — Differences of the Directions of Motions of the Lower and Upper Currents of Air, as 

 deduced from the Comparisons of the Direction of the Wind, and the Motions of the Clouds, 

 for the Years 1843-6. 



Currents, 



Quadrant N. to E. 



Quadrant E. 



toS. 



Quadrant S. 



to W. 



Quadrant W. 



toN. 



No. of 

 Results 



Mean 

 Diffs. of 

 Motion. 



Mean 

 Result. 



No. of 

 Results. 



Mean 

 DifFs. of 

 Motion. 



Mean 

 Result. 



No. of 

 Results. 



Mean 

 Diffs. of 



Motion. 



Mean 

 Result. 



No. of 

 Results. 



Mean 

 Diffs. of 

 Motion. 



Mean 

 Result. 



Scud minus 1 

 Wind. 1 



227 



+ 23 



° 



76 



+ 24 



° 



664 



+ 24 





166 



+ 20 



° 



111 



-25 



+ 7 



20 



-23 



+ 13 



58 



-13 



+ 20 



57 



-18 



+ 9 



12 









9 









19 









15 









Cir.-str. minus 1 



Wind. r 



64 



+ 40 





46 



+ 31 





371 



+ 40 





113 



+ 27 





46 

 3 



-51 

 



+ 2 



11 



1 



-25 

 



+ 20 



43 

 12 



-19 

 



+ 33 



38 

 6 



-35 

 



+ 11 



Cir.-str. minus 1 

 Scud: f 



50 



+ 36 





41 



+ 21 





190 



+ 27 





107 



+ 26 





52 



-37 



-1 



11 



-26 



^- 9 



61 



-18 



+ 14 



79 



-33 



+ 1 



16 









15 









34 









27 









Cirrus minus 1 

 Wind. 1 



20 

 16 



; 



+ 58 



-59 







+ 6 



15 

 



1 



+ 60 

 



+ 57 



190 

 26 

 10 



+ 45 



-23 







+ 36 



51 

 13 



7 



+ 31 



-41 







+ 15 



Cirrus minus 1 

 Scud. j 



20 

 17 



+ 35 

 -45 



-2 



18 

 2 



+ 54 

 -84 



+ 38 



107 

 33 



+ 36 

 -26 



+ 20 



81 

 33 



+ 27 

 -41 



+ 7 



2 



« 





1 









12 









13 









219. It happens frequently that comparisons of the motions of two currents are obtained when the others 

 do not exist, or are not evident from the absence of clouds within them or from the masses of clouds in the lower 

 current ; it is for this reason that the comparison of motions above, obtained from observations partly simul- 

 taneous and partly not, are to a considerable extent independent of each other ; yet it will be seen that they in 

 general confirm each other. Thus, the differences of the mean results for the first two comparisons (in Table 

 97) should give the difference for the third ; so in the quadrant S. to W. we have 33° — 20°= + 13° ; and the 

 partly independent comparisons for the cirro-stratous minus the scud-current, give +14°; and as the differ- 

 ences of the first and fourth comparisons should give the fifth (in Table 97), we have 36° — 20°= + 16° ; and 

 the partly independent comparisons for the cirrus minus scud, give + 20°. We obtain similar results in the 

 quadrants E. to S. and W. to N., but the differences of the motions are less marked. This appears to be due 

 chiefly to the greater proportion of negative results in these two quadrants. The means for the positive results 

 do not differ greatly in any of the quadrants. In the quadrant N. to E. we find all the three cloud-currents 

 positive of the surface-current, but only to the extent of 2° in the case of the cirro-stratous current ; while the 

 cirro-stratous and cirrous currents appear on the whole 1° or 2° negative of the scud-current. These differences 

 appear due to causes belonging chiefly to the sudden appearances of the north-east winds, which are chiefly sur- 

 face-winds, and are nearly or altogether unconnected with the upper currents. 



220. When we combine the results in the four quadrants for each class of comparisons, we have the fol- 

 lowing means : — 



Scud-current minus surface-current, 

 Cirro-stratous current minus surface-current, 

 Cirrous current minus surface-current, 

 Cirro-stratous current minus scud-current, 

 Cirrous current minus scud-current. 



mean of 1434 results, = + 14°-5 



mean of 754 results, = +22°-8 



mean of 349 results, =+29°-6 



mean of 683 results, = + 6°-9 



mean of 339 results, = + 13°-7 



MAG. AND MET. OBS. 1845 AND 1846. 



