362 The American Geologist. December, i904. 
cepted, perhaps, since it is contrary, in part at least, to all ac- 
cepted astronomical theories. But he who seeks a solution of 
problems presented by natural phenomena, must not pay too 
much attention to existing theories, nor must he fear the au- 
thorities ; for these will, in most cases, oppose the most self- 
evident truths, if they find their own th^sories in danger. Hi"^- 
tory teaches us that. We admit, however, that the conserva- 
tives have a perfect right to stand by and defend the old ideas 
until the new ones have been presented and established. But 
the trouble is, that many of these conservatives shut their 
eyes to the truth and will not allow themselves to be con- 
vinced. According to Flammarion the Academy of Cortona 
unanimously declared the discovery of Jupiter's moon to be an 
optic illusion; and Libri. a philosopher in Pisa, would not con- 
descend to put his eye to the telescope tO' see Jupiter's moons. 
There is nothing of the kind to be feared in the present in- 
stance, however. 
According to the nature of the excentricity, as stated above, 
it follows, that a small planet, even close to the Sun. has a 
very excentric orbit, while the orbit of a large planet, quite 
far from the Sun, has a small excentricity. The planets Mer- 
cury and Jupiter may be mentioned as illustrating this point. 
The former has an average distance from the Sun of 36 mil- 
lion miles and its diameter is 3,200 miles ; but it has an orbital 
excentricity of more than 7 million miles and varies about 15 
million miles in its distance from the Sun. The latter planet, 
on the other hand, has a distance oif 480 million miles and is 
88,000 miles in diameter, while its orbital excentricity is only 
23 million miles. It follows, thv^n, that in Jupiter's orbit Mer- 
cury would have reached an excentricity of about 90 million 
miles or more ; and that Jupiter, if he were 300 million miles 
nearer the Sun, would have no excentricity. Venus, the Earth, 
and Mars may serve as further examples tO' explam this point. 
The first of these, which has a distance from the Sun of 6y 
million miles and is of about the same size as the Earth, has 
an orbital excentricity of not quite 500,000 miles, while the 
Earth's orbit, which is 26 million miles farther from the Sun, 
has an excentricity of one and one-half million miles. The 
little planet Mars, on the other hand, which is 141 million 
miles distant from the Sun and which is only 4,200 miles in 
