190 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
a surface of any kind, it would appear of great extent to us because 
of the colossal dimensions of its globe. Wouldwe be able to see the 
heavens through the thick and dense atmosphere whose storminess we 
can observe from our earth? Let us suppose so, and then we would 
see the sun as a very small disk shining with hght twenty-five times 
fainter than as seen from the earth. That would be very meager for 
a sky so heavily clouded. Jupiter’s globe turns upon its axis once 
in nine hours and fifty minutes. The succession of day and night 
is therefore very rapid; only five hours elapse between the rising and 
setting of the diminutive appearing sun which passes rapidly across 
its sky. | 
Jupiter has nine moons but only five are visually of any importance 
nor can all be seen at the same time. Their apparent size, reckoned 
from their actual size and distance from Jupiter, shows them to be 
comparable to our moon. They are of greatly diminished bright- 
ness since the sun illumines them much less intensely. 
Suppose we now quit Jupiter to stop a moment, say, upon the 
nearest of its moons. From it the appearance of Jupiter will be 
immense because of the nearness of the giant globe as seen from this 
first satellite. Jupiter would indeed look like a formidable moon, 
one hundred times greater in diameter than our own, ten thousand 
times greater in extent of surface. 
Along with this same order of grandeur of ideas, an even more 
astonishing spectacle awaits the traveler who sets foot upon the 
satellites of Saturn, the nearest one especially. Situated in the 
plane of Saturn’s ring, this ring would appear only as a bright 
bar crossing the enormous globe of Saturn, but excessively distorted 
in dimensions by perspective, the whole system presenting very dif- 
ferent aspects than as seen from the earth. Add to this the eclipse 
of a portion of Saturn by the shadow of the rings (pl. 9), the phases 
of the enormous globe changing with the direction of the light from 
the sun, and we will still have only a partial conception of the views 
that would be presented to our eyes. If it were possible to land 
upon Saturn—and here the same doubt arises as in the case of 
Jupiter—the sky would have an aspect equally strange. From dif- 
ferent points of the globe, this sky, dotted with numerous moons, 
would be traversed by the luminous ring in varied aspects. At the 
Equator it would appear as a luminous thread passing through the 
zenith from one horizon to the other. At higher and higher lati- 
tudes toward the poles, it would appear as an arch, deformed some- 
what by perspective, and according to the season, which here are 
terrestrial years long, it would be cut by the shadow of Saturn 
itself. And further, depending upon the relative diameter of Saturn 
and the annular system and because of the marked polar flattening 
of the former, beyond latitudes 65° 11’, north or south, this marvel- 
