in its passage to the earth. Thus the light of stars of the first magnitude does not lose so much as one per cent.; but, on the other hand, stars of the ninth magnitude are enfeebled to the extent of about 30 per cent. Struve shows that, if his result is to be accepted, W. Herschel’s idea that his 40-foot telescope would show him stars seven times farther off than those visible with the 10-foot, was erroneous. He would, in fact, have been able to see little more than _twice_ as far. It will be obvious now that an enormous increase of the so-called _space-penetrating_ power of a telescope gives it in reality but a very feeble additional advantage, in fact, that, if there be absorption by the ether, we have already instruments capable of showing us, at the very least, half of the whole number of stars which any conceivable improvement of telescopes would enable us to see. 148. It would be out of place here to speculate on what becomes of the light thus supposed to be absorbed, for we have as yet no experimental bases on which to reason. We have not the least idea, for instance, what is the effect of change of temperature in the luminiferous ether. That it is practically incompressible we know; it is quite probable that it may not be sensibly compressed (if it be subject to gravity, of which we have no proof) even by the attraction of the mass of the whole earth—though, so great is the intensity of molecular or cohesive attraction, we may easily conceive that in the interior of bodies the ether may be considerably compressed. And it is not improbable that the ether, as a whole, may have, in virtue of its internal forces, a property (akin, as it were, to a liquid film) such that the gravitation action, which appears to be between particles of matter, may merely be the visible result of a tendency to a minimum of some affection of the fluid in which they are immersed. Regard the ether as we please, there can be no doubt that its properties are of a much higher order in the arcana of nature than those of tangible matter. And as even the high-priests of science still find the latter far beyond their comprehension, except in numerous but minute and often isolated particulars, it would not become us to speculate further. It is sufficient for our purpose to know from what the ether certainly does that it is capable of vastly more than any one has yet ventured to guess. 149. If we review the attempts recorded in this chapter we see how the scientific mind is led from the visible and tangible to the invisible and intangible.