23 
RESOLUTION OF FORCES IN GRADIENT CURRENTS 
It has been pointed out in the previous section that the effect of rota- 
tion tended to deflect currents to the right in the Northern Hemisphere. 
This quasi force can be represented by a vector of a certain magnitude 
which lies 90° to the right of the current. If we let the line AB, Figure 7, 
represent a more or less steady current of sufficient size to give the 
water particles a translatory path, then the effect of terrestial rotation 
may be shown by the line AC, Figure 7. Since the rotation effect 
is always present, as represented by the line AC, it follows that the 
only condition under which a current can flow, stream, and be pre- 
served, is fulfilled by a force or system of forces (when friction is dis- 
regarded) which acts equal and opposite to AC, and is represented in 
Figure 7 as the lime AK. AE illustrates the force characterized as 
due to varying mass and pressure, 
and is measured by the equated E 
values of the three variables— 
gravity, pressure, and specific vol- 
ume. It is, moreover, the impel- , 
ling force of such gradient currents 
G@. e., currents resulting from an 
obliquity of equiscalar surfaces) ; 
and it should be remarked here ¢ 
that this dr iving force is to be _ Fic. 7.—A diagrammatic front view showing the 
sought not back along thecurrent’s relative positions of the major elements belong- 
4 fe ing to asteady gradient current. AB represents 
course to a river-like source, but the path of flow of the water particles; AB, the 
it always lies on the right hand position of the forces due to Archimedean tend- 
‘s ‘S) encies which impel the current; and AC the po- 
stretching along the entire extent sition of the quasiforce of earth rotation in a 
of flow. The Gulf Stream, for ex- plane 90° to the right (in the northern hemi- 
5 sphere) of the direction of the current 
ample, as it follows a general path 
acound the periphery of the North Atlantic basin, is energized 
along the shores of Europe (a fact which is just as vital for 
its propagation) as well as receiving propulsion in the Caribbean. 
Where the velocity is relatively great, there the dynamic gradient 
is correspondingly steep, and without such energy distributed around 
Atlantic slopes, the Gulf Stream would directly disintegrate. If we 
divide gradient currents into the forces which combine to give flow 
to the water particles we have (1) dynamic inequalities due to vary- 
ing densities, and (2) the effect of earth rotation, each one of which 
acts in a plane perpendicular to the path of the moving water parti- 
cles. Since (1) and 2) lie in the same plane, and inasmuch as the 
acceleration of the closed curve ABDC (see fig. 6, p. 22) (represented 
by the line AC, fig. 7) has been determined, let us now regard the 
rectangle ABDC with respect to acceleration tending in the opposite 
direction. (Shown as line AH, fig. 7.) 
