Omaha daily bee., 1896-05-17

limit is dictated by the circumstance that
the pressure upon the stones or other ma
terials of which the arch is built Increases
with every increase of the span. Conse-
quently a point would be sometimes reached
when the pressure to which the stones are
subjected is so great that any further in
crease in span would be attended with the
danger that the structure would collapse
with its own weight. This consideration
defines the limit of the arch which could
be constructed out of terrestrial materials.
We can calculate the pressure that would
have to be withstood by the materials in an
arch such as that made by one-half Of
Saturn's ring. 1t is quite easy to prove
that this pressure would be so great that
even II the materials were many thousands
of times tougher than the toughest steel,
or any other known substance. 1t would be
utterly impossible for the ring 10 resist the
tendency to collapse. No doubt the strain
on the structure would be somewhat light
ened by the fact that the ring is spinning
round rapidly. The centrifugal force thence
arising must to a certain extent neutraliZe
the effect of the attraction of the planet.
This circumstance, though 1t may lessen.
yet 1t does not remove the difficulty, for
the ring has a very considerable width. If
the centrifugal force were so adjusted as
to neutralize the strains in the middle por-
ton Of the ring, 1t would be too great for
the inner portion, while II would not bd
great enough for the outer portion. Looked
~ va I a W piNuoN. ~ NOuli Gel
quite impossible, on mechanical principles,
that each ring of Saturn would be com
posed of a thin belt of solid material.
The explanation of the character of this
curious structure was first given by the late
Prof. ]. Clark Maxwell. He conducted this
memorable research by means OF that in
strument which is often more subtle than
the telescope of the astronomer, / mean the
pen OF the mathematician He thus showed
that the rings of Saturn must be composed
of myriads Of little objects, each SO minute
that 1t is quite impossible for us to see II
separately, at Its present distance from the
earth. These little objects are. however, in
such incalculable myriads, and they lie so
close together, that We can see the mighty
shoals which they form, though we are not
able to discriminate the individual members.
By this supposition the difficulty as to the
mechanical condition of Saturn's rings has
been found to disappear. Each OF the little
particles may be regarded as a moon or
satellite In attendance on the great planet.
Each such moon reyolves around the central
globe pursuing Its own track In complete
Independence of the movements of It's neigh
bors, every one of which is also guided
and held in its course by the supreme con-
trolling power of the mighty saturnian mass.
And now we are able to understand what
would seem otherwise quite inexplicable, and
that Is the exquisite structure OF the Grape
ring. For It is characteristic Of this most
extraordinary feature In the solar system !
that 1t is semi-transparent; in fact under
certain circumstances the globe OF the planet |
can BIO seen right through the Grape ring, |
though this ring. like the two bright rings, |
is said TO be quite thin, yet we must remem- |
Der that the thinness is Of a relative de-
scription. II Is thin relatively TO It's breadth
or to the gigantic size OF the planet, bur
In more familiar standards. the ,
rings are doubtless hundreds Of miles In
Here. then. we have a structure
Of membrane, or whatever We may call II,
hundreds OF miles In thickness which never
Iheless Is sufficiently transparent TO enable
Us to see through It. 1t IL quito plain that
he explanation We seek may he found In the
circumstances that the Grape ring. like the
utter rings. IL composed Of myriads Of small
PARTICLES. only Ia the case Of the semi-trans
,arent ring the particles are more scantily
so that we are enabled In some
Iegree to see between them. Thus we can
for the Characteristic feature Of the