DIASTROPHISM AND THE FORMATIVE PROCESSES 129 



II. The material factor of every cosmic unit is not only per- 

 vaded internally but is surrounded by a field of force, domi- 

 nantly attractive but partially repellant. In the present study, 

 the sphere of dominating attraction — the sphere of gravitative con- 

 trol — will, for brevity, usually be spoken of as though it alone 

 represented the dynamic element of the dual organization, for it is 

 chiefly the outlying field of gravitative control that functions 

 actively in the selective segregation of material in the formation 

 of cosmic bodies. 



The extreme theoretical reach of gravitation is indefinite, but 

 within a certain portion of this indefinite field, the attractive 

 force of the particular body under study is sufficient to give it 

 immediate control over bodies inferior to itself, unless they carry 

 kinetic energy of their own in sufficient amount, and properly 

 directed, to insure their escape. This field of superior force 

 constitutes the body's sphere of control.' It is necessary to note 

 that this control is merely immediate control; there are usually, 

 perhaps always, higher types of control which hold ulterior sway 

 over these, but this superior sway is exercised in such a concur- 

 rent way as not to prevent the immediate control essential to the 

 minor body as a condition of its own existence and perpetuity. 

 These higher controls may spring from some single more massive 

 body or from some composite organization, as a star group. The 

 superior spheres of control envelop the minor spheres of control; 

 thus the moon's sphere of control revolves within that of the earth ; 

 the earth's sphere of control revolves within that of the sun; the 

 sun's sphere of control revolves within the sphere of control of the 

 "local cluster" of stars, and this in turn within the sphere of 



' The recognition that cosmic bodies are surrounded by spheres of gravitative 

 control is not at all new but merely neglected; Laplace worked out "the spheres of 

 activity" of the planets — here called spheres of control to avoid confusion with the 

 indefinite outward extension of the influence of the cosmic body. The spheres of 

 control of the planets have been worked out more recently on a different basis by 

 Moulton {Popular Astronomy, No. 60, May 15, 1899). The spheres of equal attrac- 

 tion, a different matter, have been worked out by the senior Asaph Hall {Popular 

 Astronomy, April, 1899). The concept of a sphere of control is herein given a wider 

 application than is common, and is assigned an essential function in the organization 

 and maintenance of cosmic bodies. The concept is regarded as a helpful means of 

 research, particularly as an aid to visualization. 



