New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1898-12-09
uction Of other factors and to reAnements Of

duction Of other factors and to rehnements Of
methods.
1t is easy for the me-est child to understand
some Of the theories that have been advanced
regarding the tides. one can see how the at
traction o: the and moon might lift up a
considerable bunch Of water on that side of the
earth which is nearest to those bodies; that the
influence Of the SUM- though ii is by far the
larger. should be a trine less than half as great
the moons. because the moon is very much
nearer to US; and that when the sun and moon
pulling together. as a. the time OF new moon
and fun moon. a higher rise should be produced
than when the sun and moon are about ninety
degrees apart in the heavens. But it is more
difficult to see why tn IRE should be two high
tides every day instead Of only one. That gravi-
taton should bank up huge mass of water
on one side of the globe is ineligible enough;
but why is another ma lifted up the OPP
posite side, simultaneously? Professor Darwns
explanation is rather more sati factory to the
lay mind than some that have been offered In
the first place is to remember that the
moons attraction is exerted upon all particles
Of the earth and its watery envelope. And this
attraction varies the cube Of the distance.
The distance from the centre Of the moon to the
centre Of the earth lin round numbers, two nun
dred and forty thousand niles is sixty times the
radius OF the latter body. The side OF our globe
which is nearest to the moon at any given mo-
ment is only ffty-nlne radii away. and the region
the opposite side is sixty-one radii distant.
The moon pull Of the satellite on the further
side. then. Is not so great as 1t Is upon this side.
Another fact must now be taken into considera-
ton. Although accustomed to speak OF
The moon revolving about the earth both bodies
are really revolving about a point that lies be-
tween their centres. Thu common centre OF
gravity OF the pair lies about 1900 miles from
the earths centre and Z37 900 miles from the
centre Of the moon. The additional 1900 miles
Of terrestrial radius makes the distance Of the
side of tie earth away from the moon about
1000 miles from the pivotal PORT. One arm OF
this imaginary lever Is very much shorter than
the other. yet centrifugal force will be devel-
oped 1T both extremities. or course the ten
dency TO fly of into space will not be as great
III the one case as in the other hut 1t Is impossl-
| ! lie that sling I,Oo0 miles org shall be rapidly
swung around central point without producing
a marked tendency to repel object the
outer end. 1t is centrifugal force. then. accord
! ing TO Professor Darwin. that throws up that
mass Of water on the further side of the earth
| And though the moons attraction serves to
counteract this tendency TO some extent, II must
! be remembered that that attraction is less pow
erful at a distance of sixty radii than at
| ffty-nine.
| The alienation OF land and water on the
earth's surface interferes with the progress Of
tidal wave that tries to follow the moon
around the globe at the rate of over one thou
J sand miles an hour The observed facts are
very different from the dictates OF theory there
fore. For instance. tide that sweeps across
J the Southern Indian Ocean from Australia to
the Cape OF Good Hope divides at the latter
point. One part continues to travel in a west
erly direction toward Patagonia and the other
moves northward up the Atlantic. The latter
| portion. reinforced by newly born tide formed
! between Africa and South America, takes twelve
| hours TO advance from the Cape to the coast Of
| New-Jerscy. Ne H-England and Nova Scotia
| The eastern wing Of the Atlantic wave sweeps
| on toward Ireland and Norway. arriving six
| hours later In the vicinity Of the former. and
| twelve on the coasts Of the latter IT order 10
predict the time Of the high water at any place.
one must make series OF observations. But an