wo-hundredth part of the former
estimate.[356]

Astronomers have lately been comforting the world with the assurance
that we have little to fear from comets; that the superstitious fear of
the comets prevalent in the past was ill founded, because comets are so
very thin that we might pass through one without its breaking up
anything. But that, as Principal Leitch shows us, is not the only
question. "We know that the most deadly miasmata are so subtle that it
is impossible to detect them by any chemical tests, and a very
homeopathic dose of a comet, in addition to the elements of our own
atmosphere, might produce the most fatal effects."[357]

The phenomena indicative of cosmical processes are out of the range of
astronomical observation. We can only observe those indicated by light,
and gravitation; but how small a proportion of the formative processes
of our own world indicate themselves by these two classes of phenomena!
How few of the chemical, vegetative, animal, moral, social, or even
geological processes, now progressing under our own observation, could
give us notice of their existence by the two channels of light and
gravitation? How, then, can philosophers ever learn the process of
building worlds like our own in which many other powers are at work?

Astronomers are not all agreed as to the existence of a cosmical ether;
nor do those who assert it agree as to its properties. What is its
nature, density, power of refraction and reflection of light, and
resistance to motion? What is its temperature? Is it uniform, or like
our atmosphere, ever varying? These are manifestly questions
indispensable to be answered before any theory of the development of
worlds is even conceivable. But of the properties of this all-extending
cosmical atmosphere, which is the very breath of life of the development
theory, astronomers present the most conflicting statements. Professor
Vaughan says, "If such a body exists, it is beyond our estimation of all
that is material. It has no weight, according to our idea of weight; no
resistance, according to our idea of calculating resistance by
mechanical tests; no volume, on our views of volume; no chemical
activity, according to our experimental and absolute knowledge of
chemical action. In plain terms, it presents no known re-agency by which
it can be isolated from surrounding or intervening matter."[358] Or, in
plainer terms, we know nothing about it.

The only fact about it which ast