104 GENERAL DESCRIPTION OF THE MOON. 



Moreover, the surface of the moon reveals much to the naked eye, 

 not clearl}^, })ut sufficiently well to afford the basis for speculation and 

 to tempt the imaoination to create there a world like our own. It is 

 therefore not surprising that a host of myths concerning the nature 

 of our satellite grew up in the days before the telescope. It is inter- 

 esting to note the fact that many of these myths have not only become 

 fixed in the minds of uninstructed people, but they have had a remark- 

 able influence upon modern astronomers, limiting their capacity to 

 interpret what their instruments clearh' reveal to them. At every 

 stage in the advance of selenography we note the curious persistency 

 of the endeavor not only to interpret the lunar features by the terres- 

 trial, but to warp the observed facts into accord, with those seen on 

 the earth. There is perhaps no better instance of the extent to which 

 prepossessions and prejudices may affect the judgment of the most 

 conscientious observer, blinding him to evident truth, than the history 

 of lunar inquiries affords. 



The story of the physical conditions of the moon had best be begun 

 by noting that the relation of our satellite to a larger sphere is not 

 exceptional, but the most characteristic of all the relations of one stel- 

 lar body to another. Of the planets in the solar system, all save the 

 two nearest to the sun. Mercury and Venus, have one or more smaller 

 spheres circling about them. The relation of the sun to the several 

 planets in a larger way repeats this plan of grouping lesser about 

 greater orbs. 



It is generally believed by astronomers that the celestial spheres 

 have been formed by a process of condensation, due to gravitation, of 

 matter which was originally widely diffused; that our solar system, 

 before it was organized into the sun tuid lesser bodies, was in the form 

 of a diffused nebulous mass of spheroidal form which extended beyond 

 the orbit of the outermost planet. As this matter gathered toward 

 the center, the material now in each of the planets and its satellites 

 parted from the parent body, probably at first in the form of a nebu- 

 lous ring, or spiral, which in time broke and gathered into a spheroidal 

 mass. In that detached portion of the parent nebula the process of 

 concentration was repeated, with the result that satellites, or, as we 

 may term them, secondary planets, were formed substantially as the 

 greater spheres were set off from the sun. There are many questions 

 and doubts concerning the details of this nebular theory, but that the 

 evolution of our solar system, and probably of all stellar systems, took 

 place in substantialh' the manner indicated appears to be eminently 

 probable; it is, indeed, fairly well established by what we know of the 

 distant nebulae and by the rings of Saturn, which apparently contain 

 the material which normall}' should have formed one or more of its 

 satellites, but which for some unknown reason have remained 

 unbroken. 



