In Professor Proctor's article ("Essays on Astronomy") on the square-shouldered aspect of Saturn, he mentions a hitherto unexplained circumstance of the earth's atmosphere--the curious fact that the barometrical pressure of the earth's atmosphere is somewhat higher between the poles and the equator than immediately over the latter, as might be supposed to be the case. This is a phenomenon of mutual repulsion similar to those manifested in the operations above described. The rotation of the earth on its axis forces the terrestrial atmosphere, by its centrifugal motion, in undue proportion, around the equatorial belt, causing the same sort of atmospheric thinning at the poles which we see in the solar photosphere at its corresponding parts. At the same time the highly electrified atmosphere, by its mutually repellent action, tends to force this swollen equatorial ring backward toward the poles. The resultant of these two repulsions is an area of maximum density part way between the poles and the equator. It is probable that this self-repellent equatorial swell may play some part in the sun's atmosphere, in extending, and also in limiting, the areas of eruptive sun-spots outward from his equator. While the nebulæ are more distant than many of the discrete stars revealed to us by the telescope, there is no reason to suppose that they are more distant than the star-clouds into which are merged the separate stars of the Milky Way, or the star-clusters seen in other portions of the sky. We know, in fact, that this is not so, for our telescopes show brilliant stars in very many cases which are components of the nebulæ themselves; and the fact that the nebulæ can be seen as having visible form, and not as mere points of light, is itself conclusive as to their relative distances. Hence we need not be surprised to learn that these forming spirals will result each in the production of a single solar system, and not a galaxy of suns, as was once supposed. Were such the case it would be impossible for us to observe the structure of the nebulæ at all, as their distances would be far too vast. Of the forms of the gaseous nebulæ Guillemin asks, "Is the spiral the original form of those gaseous matters, the condensation of which may give, or has given, birth to each individual of this gigantic association?" The same author says of these apparently regularly formed nebulæ, "It is impossible not to recognize in them so many systems." Many of the spiral nebulæ were formerly supposed to be globular aggregations of nebulous matter only, and their spiral character came as a great surprise with the use of more powerful telescopes; and many--nay, most--of these apparently globular nebulæ have totally changed their appearance when viewed with instruments of higher power, while the spirals have become more and more pronounced in character with every increase of telescopic vision. Of one of such apparently globular nebulæ Guillemin says, "The