Page:Popular Science Monthly Volume 18.djvu/879

Rh of every great dissemination of matter where the different members of the mass exercise a mutual attraction upon each other at a distance. M. Faye admits that in the transformation of the nebula rotatory movements would take place, and that trains of matter analogous to the rings of Saturn might be formed, and might break and give rise to planets. These formations, he believes, could be divided, according to their relations to the gravitation of the mass, between two zones, in the outer one of which the revolutions would, by the regular operation of the laws of gravity, be retrograde, while in the inner zone they would, under the same laws, be direct. This is shown to be possible by the following considerations: The density in the original nebula increases regularly from the periphery to the center, as appears actually in several nebulæ with which we are acquainted. It has been shown by calculation that the force of weight in a mass thus constituted increases, as we depart from the surface, in the inverse ratio of a power of the distance from the center. This progression, however, soon reaches a maximum, after which the weight is proportional simply to the distance itself, till at the center it is nothing. If we suppose planetary rings to be separated from a nebula of this nature, we may see that those separating from the external region will be of such a character that the motion of their outer circumference will be more rapid than that of their inner circumference, so that, when it is reduced to a globe turning upon itself, the globe will move in a retrograde direction. In the rings found in the second or inner region, on the other hand, the relative rapidity of the motion of the greater and lesser diameters will be reversed, and the rotation of the resultant globe will necessarily be direct.

Infertility in France.—The population of France has increased very slowly for several years. Among nineteen principal states of Europe, France stands the lowest in the rate of growth, having shown an annual increase of only 3·16 per thousand inhabitants from 1861 to 1869, while such countries as England, Norway, Scotland, and Russia, show an increase of from 12·94 to 13·85 per thousand. The rate of increase has fallen from six per thousand in 1770-'85, and has never since risen to that figure. The smallness of the excess of births over deaths, which is measured by the rate of increase, is due solely to the paucity of births; for the mortality has at no time been excessive, and has diminished steadily in the face of wars and epidemics, except during the German war, since the beginning of the century. It is not accompanied by a diminution in the number of marriages, for the proportion of marriages has not undergone any material variation during the century, and was higher in the sixth decade than in the first. Moreover, France outranks in the proportion of marriages to the whole population, and of marriages to the marriageable population, some of the states which greatly exceed it in the rate of increase of population. M. A. Legoyt has investigated the subject, and assigns the infertility thus shown to various moral, political, economical, and physiological causes. The decay of religious beliefs is a cause, the influence of which is shown in the tolerance given to the voluntary limitation of fertility, which is opposed by every religious system, and the increase of illegitimate unions, abortions, still-born, and infanticides. The unusually large proportion of persons who are just well enough off to be carefully provident is economically unfavorable to fertility. The popular opinion that poverty and children go together seems to be confirmed in France, where the poorer departments are the more fruitful ones. Other economical influences are the tendency of population to cities, the increasing expenses of living, and the system of dividing the paternal estate among all the children, which offers a standing temptation to the parent to have only a few children, so that each shall have as large a share as possible. The destruction caused by war operates powerfully to cut down the population. It is worse than pestilence, for it takes away the best and most vigorous. France has suffered much by wars during the last century, and has lost heavily at several periods, most notably during the two years of the German war, when the deaths considerably exceeded the births. The statistics of the recruiting officers show, however, that the vigor of the race has not