CIV 
General Results of the Makerstoun Observations. 
It appears, then, that if we take the mean direction of the surface-current as W. 21° S., the directions of the 
four currents will be nearly as follow : — 
Resultant direction of the surface-wind (No. 207), W. 21° S. 
•• scud-current, W. 7° S. 
cirro-stratous current, W. 2° N. 
cirrous current, W. 9° N. 
The mean resultant direction for the three cloud-currents, giving each an equal value, is W. 1° N. The mean 
resultant direction of all the currents, giving each an equal value, is W. 4° S. 
221. If we neglect the distinctions of the upper currents, and consider merely the differences of all the 
results for the cloud-currents compared with the surface-wind, we obtain the following numbers : — 
Quadrant N. to E., 499 results, mean upper current mimes surface-current, = + 5°-8 
E. to S., 179 =4- 19°-1 
S. to W., 1393 = +26°-6 
W. to N., 466 = + 10°-6 
The mean upper current, therefore, is least positive of the surface-current in the quadrant N. to E., and it is 
most positive in the quadrant S. to W. ; the mean result for each couple of opposite quadrants is nearly the 
same, namely, 15° and 16°. 
222. If we compare in a similar manner the mean cirro-stratous and cirrous current with the scud-cur- 
rent in each quadrant, we have, — 
Quadrant N. to E., 157 results, mean cirro-stratous and cirrous current minus scud-current, = — 1'^'2 
E. to S., 88 = + 15"-9 
S. to W., 437 = -Hl6^"-1 
W. to N., 340 = + 3°-2 
In the quadrant N. to E. tlie mean of the two upper currents seems to differ nothing from the scud-current, and 
nearly the same seems to hold for the quadi-ant W. to N. ; but in the southern quadrants the mean upper cur- 
rent is positive of the scud-current 16°. 
223. It appears, then, from the previous numbers, that the mean upper ciu-rent always proceeds from a point 
positive of the direction of the surface-ciwrent, and that the motion of the mean of the higher currents, compared 
with the motion of the scud-current, obeys the same law in the southern quadrants. These results are in accord- 
ance with the conclusions from the causes of the oblique motions of the aerial currents. Currents of air pro- 
ceeding northwards from more southerly positions retain a portion of the excess of eastward velocity of the places 
from which they start ; hence the south-easterly winds become more southerly, and the south winds become more 
south-westerly, as they proceed northwards ; the extent of the change of direction depending on the greater or 
less rapidity with which they lose their excess of eastward velocity and acquire that of the more northerly lati- 
tudes on which they move. This loss of eastward velocity ^^^ll depend upon the proximity of the aerial stratum 
to the surface of the earth, and therefore the lower currents of air will lose more of their eastward velocity tlian 
the higher currents, and the upper current of southerly ^nnds will become more westerly than the lower cur- 
rents. If, in considering the currents of air which proceed southwards from more northern latitudes, we re- 
member that the lower currents, from their proximity to the surface of the earth, acquire the greater eastward 
velocity of the lower latitudes more quickly than the upper currents, it will be evident that the lowest cm-rout 
from the north-west should become less northerly than the upper current, aud that the lower current from t!io 
north should become less easterly than the upper current. This, it will be observed, agrees with the results 
previously obtained ; we find, however, in the northern quadrants, that the scud-current differs loss from the 
surface-current than it does in the southern quadrants ; this, it is conceived, is due to the fact that this current 
is nearer the surface in the northern than in the southern quadrants : it may, however, be due also to the 
greater proximity of the origin of the currents. We find also that the mean upper currents differ little or 
nothing from the scud-current in the northern quadrants ; it is only necessary to examine the numbers in Table 
97 to sec that this is not due to the smallness of the diiferences of motions of those currents, biit to the num- 
bers of positive and negative results being nun-o nearly 0(iual. It lias boon frequently observed that when the 
lower current of scud is from a north-easterly point the current of cirri is from a north-westerly point ; these 
currents could not have had the same origin, and therefore the explanation of the differences of motions gi^en 
above cannot apply ; this difference of origin occurs in all the quadrants, and diminislics the apparent ellect of 
the variable velocity of the earth's surface ; it occurs soldomest in the south-west quadrant. 
