relative to the Earth's Surface. 29 
v is the velocity of a body moving in any direction 
whatever, and F the deflecting force perpendicular to this direc- 
tion, by ‘yesolving the preceding forces and velocities in the 
direction of v and the perpendicular to it on the right, we get 
(5.) F= 2nv cos 6. 
In the northern hemisphere cos 4 is positive, but in the south- 
ern negative. Hence, we have established this important prin- 
ciple, in whatever direction a body moves, wt is always deflected to 
the fate in the northern hemisphere, and the contrary in the southern 
hemis 
The fovien resolved in the direction of v cancel each other, and 
hence the velocity is never accelerated or retarde 
ince rn? represents the centrifugal force at the equator 
arising from the earth’s rotation, and is ‘known to be sty Of g or 
gravity, the preceding equation may be reduced to 
2v cos 
(6.) = 9800 
This form of a equation is convenient for comparing the 
force F with gra 
7. In the eonalies equations rn is the lineal velocity of the 
equator, sa is Pot to 1523°2 feet, the : second being the unit of 
="000072924. Also feet. 
It may be feniaked here that the areoelied deflecting force is 
not an. absolute seg such as would be required to deflect a 
moving body fr a fixed direction in space, but is only rela- 
tive, being minieahia of the nature of a centrifugal force, and 
from the fact that the direction relative to the earth to 
which the moving body is referred, is co ——s changing its 
direction with regard to fixed directions in space. 
Il. The general Motions and Pressure of the Atmosphere. 
8. By the Sees och Caio of the atmosphere are meant all 
those motions produced by a difference of density between the 
equatorial and polar regions arising principally from a difference 
of temperature. If the mec in all parts of the earth had 
the same density, every part would be in a state of statical equi- 
librium, and its surface and “te strata of equal density wou 
assume the elliptical figure of the earth’s surface, and conse- 
quently the -pressure of the atmosphere at the earth’s surface 4 
ene 
would be everywhere the same. But the temperature of the at- 
mosphere being less and consaguesth its density greats , the 
ec than the equatorial e greater pres ae 
o3 ar regions causes the areas of ‘the atmosphere @ and 
of equal density in the equatorial regions to rise a. tle a “peel 
the level of equilibrium, and hence the atmosphere in the upper 
regions flows toward the poles, while ae greater pressure 0. of the 
