William Henry Farquhar

“ The richest parts of the sky, in bright and faint stars alike, are almost all about the Milky Way. This stream of suffused light follows, with some irregularities, the course of a great circle; and toward the plane of this circle, passing not very far, perhaps, from the sun, stars at all distances appear to become more densely packed. The Milky Way itself is evidence of this for the faintest magnitudes; and Herschel's star-gauges, from which he inferred for our cluster the shape of a disk or lens, give the comparison in a numerical form. ”

“ It is very certain that an equable distribution could not hold throughout all space (for an infinite number of stars impartially scattered would, however vast the distances among them, give us a heaven shining like the sun in every part, with heat to correspond) unless, owing to the presence of innumerable dark bodies, or to a discontinuity in the luminiferous ether itself, as some physicists have suggested, light from remote distances is wholly or partly cut off before reaching us. ”

“ The conclusion seems unavoidable that a uniform distribution of stars does not hold even in the region of space immediately about our solar system. Since the ratio of number is smaller than it should be to correspond to that of light, the density in which the stars are aggregated—if the expression be permitted—must diminish as the distance increases. Our sun is therefore in a part of space more closely filled than are neighboring parts. ”

“ The idea that each observer has of the meaning of second or fifth magnitude is derived entirely from tradition and confirmed by habit, very much as are his notions of the significance of ordinary adjectives of degree—the only precaution observed being to alter the estimates of antiquity as little as possible, a vague limitation at best. Measures with the photometer depend no less on estimates with the eye, but the determination in them, as to the exact agreement of two lights, is subject to far less uncertainty. ”

“ It is not easy to make out, from the general distribution of the stars, that our sun is in one direction rather than another from the center of the sidereal system, and there is even some doubt about the position which some astronomers give us, on the northern side of the plane of the Milky Way. Indeed, beyond the prevailing condensation toward this plane, it seems that no important general law governing star aggregation has yet been found. ”

“ It must be just as easy to tell a fourth magnitude star, for instance, from a fifth magnitude as from a third, and there must be as little doubt in distinguishing between the fifth and sixth magnitudes as between the third and second. The numbers expressing magnitudes, then, must actually represent a scale of equal differences as measured by the sensibility of the eye. ”

“ The same division into thirds of a magnitude is still employed by those who judge of brightness by eye estimates, though some are content with dividing into halves, and some undertake to be exact to tenths. Now, even though no scientific precision was attained, or even thought of, in this original apportionment of visible stars among the six magnitudes, to which all later estimates are adjusted, we would expect to find one principle underlying such a classification, making it that of greatest convenience. ”

“ And if astronomers have hitherto interested themselves less in questions of precedence and seniority than in the particular spot on the field occupied by each individual in the great array when drawn up for review; if, dropping the figure, differences of luster and the number of stars of the various grades have occupied less of their attention than the comparatively dry details of right-ascension and declination, with all the refinements of precession, nutation, aberration, proper motion, parallax, refraction, etc., affecting these—they are now making some amends for their neglect. ”

“ The proof advanced is always incomplete, resting on assumptions not generally admitted; and when we remember that the gravitative force exerted by the fixed stars on one another is so small that to keep the nearest of them from falling to the sun, supposing no counterbalancing attractions, an angular velocity of but one second of arc in eighty years is needed; that the proper motions to be explained are often far larger than this; that the distance of the attracting center must be many times that of the nearest fixed star ”

“ THOSE who view and admire the starry canopy above us—so fittingly associated, in the oft-quoted language of a great philosopher, with the moral nature of man—can hardly fail to remark how largely their pleasure in the grand prospect is due to the endless variety in its brilliancy. ”

“ That such a limitation exists we have other reasons for believing: prominent among these is the system of distribution which a census of the heavens brings to light. We could not expect an infinite universe of stars to show everywhere such a uniformity of plan.
How the fixed stars are actually distributed through space, an inquiry into which we are led by study of their number and brightness, it has been but recently found worth while to consider. ”

“ The sun, it would seem, is to be considered as in a region of exceptional rarity as compared with other regions through which the galactic plane passes, and at the same time of exceptional density when the comparison includes stars remote from this plane. ”

“ Peirce found the same ratio to be only as 4 to 3. He was also surprised to see that the stars were very little more numerous in the track of the Milky Way than at a distance of 20° from it, the decrease in density appearing almost suddenly about 30°. But as we approach the sun, the rate of condensation becomes greater again. Of the twenty stars classed as first magnitude by the best observers, fifteen are within the 30° circles; and of the five outside, but two, Arcturus and one far southern star, are equal in brightness to the average of the twenty. ”

“ If I am carrying a small weight, for example, and the addition of an ounce is required to make the burden perceptibly heavier to me, two ounces will have to be added in order that I may notice a difference when I carry twice the weight, and a whole pound when I carry sixteen times the weight. ”

“ And we know something more: if in the northern hemisphere—a limited part of the heavens must be taken for the purpose, few catalogues being complete in southern stars—he classes 200 stars in all as brighter than 413, while he calls 25 stars 413 exactly, he means to tell us that his 413 magnitude stars would all fall between 200 and 225 on a list of northern stars arranged in order of brightness. ”

“ The stars thus appeared as two disks, of different sizes but equally bright, and the amount of light given by each was taken as proportionate to the area covered by its disk. The same Dr. Zöllner who has lately become so conspicuous in "spiritualist" investigations, invented a much more convenient style of photometer, with which he made some interesting researches into the comparative light of the planets. Other astronomers, European and American, have also used it. ”