6 FORMATION OF THE EARTH 



charged with negative electricity. They are arrested at the 

 surface of the network, where their tension increases till they 

 finally launch across the whole extent of its surface electric 

 discharges which would illuminate it, just as such discharges 

 illuminate a Crookes' tube. This would have been the origin of 

 the nebulae whose temperature, in spite of their phosphorescent 

 condition, would be more than 200 degrees below zero. The 

 spectrum of these nebulae shows bands of helium, hydrogen, 

 and certain apparently special elements. When a particle of 

 matter, however small, penetrates such a nebula, a fragment 

 of a broken star, for example, like those which form 

 meteorites, it at once becomes a centre of attraction towards 

 which the particles of the nebula hurl themselves and eddy 

 round it, developing at the same time a terrifically high 

 pressure and a very intense heat. The cold and phosphorescent 

 nebulae thus become transformed into a gaseous and in- 

 candescent mass, a kind of vast flame convulsed by movements 

 of incredible violence, at first entirely disordered. Gradually, 

 however, out of this very disorder, out of the collisions and 

 partings which ensue, a kind of harmony is born. These internal 

 movements become, so to speak, classified ; some are reduced 

 to simple vibrations propagated in the form of different 

 radiations across the ether far removed from the nebula ; 

 others are fused in a single rapid rotatory movement, dragging 

 along with them the entire mass of the nebula, compelling 

 it to revolve at a prodigious speed around a single ideal axis. 

 It must be admitted that, strictly speaking, the original 

 diversity of the movements divides the nebular mass into 

 several unequal parts, each whirling around on its own account, 

 with a translatory movement which is transformed into a 

 rotatory movement of the small masses around the larger 

 ones by which they will be attracted. It is thus that a system of 

 luminaries such as the multiple stars might have arisen directly. 

 For our solar system, however, Laplace was led to another 

 hypothesis, grandiose in its simplicity. 



The incandescent nebula would, in his view, consist only of 

 a spheroidal mass revolving in its entirety, at an inconceivable 

 speed, round an axis. In conformity with the laws of centrifugal 

 force this mass, by reason of its speed, would assume an 

 ellipsoidal form such as that of the earth. The region corre- 

 sponding to the equatorial zone would then, at the successive 



