DIASTROPHISM AND THE FORMATIVE PROCESSES 497 



resented in Table II, the sizes of the spheres of control will remain 

 about as given whether the substance they contain takes the form 

 of an expanded gas, or an open swarm of precipitated granules, or 

 a compact solid body. This puts everyone in the way of modifying 

 at pleasure the illustrations I offer. 



To the concrete pictures already given the following may be 

 added as now more immediately serviceable. From the minimum 

 radius of the sphere of control of the earth, 620,000 miles, let a 

 depth of 20,000 miles on the outer border be left essentially unoccu- 

 pied and the whole present substance of the earth distributed 

 uniformly throughout the remainder. It would have a density 

 of o . 001 266 on the air standard. In the form of a cloud of granules, 

 each half the mean density of the earth, and distributed uniformly, 

 the empty space about each granule would be over a million and a 

 half times the space occupied by the granule itself. 



If a lo-mile planetoid were converted into a cloud of granules 

 uniformly distributed through its sphere of control, the cloud 

 would have a density of o .00111 on the air standard. If the gran- 

 ules had the same density as in the planetoid, the average empty 

 space about each granule would be more than two million times the 

 volume of the granule itself. 



If therefore the clouds of granules were quite diffuse, they yet 

 might be controlled by their mutual gravity, provided the dis- 

 persive components of their internal movements were negligible. 

 But with such wide distribution any appreciable dispersive move- 

 ments would be fatal to control. 



To fashion a case of this order with a working margin of space, 

 let the matter of a lo-mile planetoid of density t^.t^ be dispersed 

 uniformly as granules of like density throughout the central f 

 of its sphere of control, leaving the remaining | as empty space 

 which the granules must cross to escape. The density on the air 

 standard would be o . 00889, while the average empty space surround- 

 ing each granule would be 280,000 times the volume of the gran- 

 ule itself. Even in this case the velocity at the surface that would 

 give escape if directed outward would be perilously low, not above a 

 fraction of an inch per second. This reveals the critical nature of all 

 this class of cases. To insure success in final concentration, the 



