Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1919-08-16
Scientific Discussions
by Garrett P. SerUiss
BY GARRETT p. sERvIsS

BY GARRETT =. SERVISS
Here are two questions to which
the asker says he can get no an-
swer:
Cd eff a vertical line to Nsw
York be extended through the earth
adnade to project from the other
side, will this projecting line be Il
vertical line?"
CD "If a running siphon De
placed under the receiver of an air
pump, and the air be exhausted to
one-t tenth, how much more slowly
will the siphon run than when un-
der full atmospheric pressure?"
/ cannot undertake to answer all
questions of this kind, but only
those which, like the above, involve
broad principles and facts which il
would be useful and interesting to
everybody to know. They are Of
the nature of the mental food on
which Isaac Newton nourished the
, beginnings of the mightiest scientific
intelligence ever developed by a hui
man being, as when, for instance,
| in his boyhood, he undertook to
measure that force of the great tenn
pest that roared over EnglaAd on
the day that Oliver Cromwell dioG
by jumping first with the wind and
| then against it.
Cd A vertical line at New Yol
extended straight through the earth
would not except by a miracle of
chance, be vertical line at the
point where it emerged. 1t would DE
vertical if the earth were an abso-
| lutely perfect sphere, of uniform
| density throughout, because then ii
| line which was vertical at any point
| on the earth would be vertical at
any other point, since all such lines
would necessarily meet exactly ct
| the center.
| But the earth is only approXl-
mately a sphere, or, more nearly,
| an ellipsoid, with the line through
| it's poles of rotation serving as the
minor axis. Or it may be called an
! oblate spheroid i. e., a solid re-
sembling a sphere, slightly fiattened
| at the poles.
In truth, the most careful inves-
! legations of the earth's shape prove
that it does not perfectly accord
with any regular geometrical solid
| The consequence is that lines which
| are vertical to it's surface at one
point may not be vertical if trans
! ferred, without change of direction
! to another point. In other words
! such lines would not all pass
| through the center.
| Then, too, the direction of tte
! plumb line at any place on the
earth is not determined solely by
the attraction toward the center OF
| gravity, but in part by the centri-
fugal force due to the earth's rota-
ton, and this force varies with the
distance from the equator. More
| over, the substance of the earth's
interior is by no means of uniform
density, and variations of density
cause corresponding differences III
the direction of the plumb line.
| There are places where the
| plumb-line falls as much as ten
| seconds of arc aside from the pu
sition that it would occupy if the
rocks below and all around were OF
uniform density. Some of these
cases are very puzzling, indicating
/ the existence of surprising centers
of local condensation, or masses OF
strangely heavy material lying al
no great depth below the surface.
There is a place on the coast ot
Scotland, in the County of Banff
where the mysterious local attrac-
ton is so strong that the romantic