96 KANSAS CITY REVIEW OF SCIENCE. 
A COLOSSAL ENGINE AT WORK FOR MAN. 
EDGAR L. LARKIN, 
It is known that if a balance-wheel revolves, the mass of the rim draws against 
the centre, if the wheel is heavy and in rapid revolution, the spokes restrain a 
powerful tendency of the circumference to break in pieces and fly away on tangent 
lines. Or, if we revolve a grindstone too rapidly, it will burst into fragments, 
each being hurled away on straight lines with great force. Indeed, should we 
have a solid mass of steel in the shape of a disc, say twenty feet in diameter and 
five feet thick, and hung on an axis, it could be burst in pieces simply by causing 
it to revolve with sufficient velocity ! We are all familiar with this tendency 
called the centrifugal, and recognize it as being one of the most powerful energies 
developed by motion ; while with the indulgence of the reader, we desire to pre- 
sent one of the most magnificent examples of its action, in the endeavor to impress 
the mind with some idea of nature's grandeur. We will present the case in its 
most elementary form, and ask that the student will follow in a computation that 
we promise shall not offer difficulties. 
I St. The acceleration due to the centrifugal tendency of a moving body, is 
equal to the square of its velocity divided by the radius of its path. Let us take 
a rod of steel five feet long, attach one end firmly to an axis, and the other to a 
cannon ball whose weight is fifty pounds, then revolve the axis fifty times per 
second and compute the acceleration due to the centrifugal tendency. Since the 
radius of the circle traversed by the cannon ball is five feet, its circumference is 
31,41 feet; and since the ball makes fifty revolutions per second, its velocity is 
31 4iX5°=^57° ^^^*- P^'^ second. By the rule — 1570 squared=2,464,900 which 
divided by 5=492980 feet as the acceleration. 
2d. The entire centrifugal tendency is equal to the acceleration multipHed 
by the mass of the body, and tension on the steel rod is proportional to the accel- 
eration and gravity. The mass of the cannon ball is fifty pounds and the inten- 
sity of the earth's gravity is able to impart to a falling body a velocity of 32.2 feet 
per second at the close of the first second of fall. Therefore: — 492,980X50= 
24,649,000 which divided by 32.2=765,496 pounds tension on the rod! What 
bar of steel could withstand this enormous force ? We see what tremendous 
power is developed by rotary motion, for here is a force of 383 tons evolved in a 
simple machine capable of being run in any of our manufactories, and moving 
with a velocity of only 1570 feet per second ! Now let us make application. We 
will take a rod of cast-iron 92,882,917 miles long and fasten one end to a sphere 
whose diameter is 866,394 miles, and the other to a ball 7925 miles in diameter 
and set the machine in revolution. To the small ball we will impart a velocity of 
not a few feet, but a rate of 97,642 feet or 18.4927 miles per second. When the 
vast engine has attained its full speed, and is in revolution in regular circuit, then 
