30 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Mar., 1904. 



duced by retiection from the edf,'es of the coins, these 

 had been painted with non-actinic colour. 



Finally, it was thought that the coins might have been 

 thrown into a state of agitation, and had mo\-ed daring the 

 passag'e of the current, and to exclude this possibility 



trend taken by speculations as to its origin. They have 

 become more subtle, more far-reaching, yet less confi- 

 dent. They have ramified in unexpected directions, but 

 rather tentatively than with the full assurance of attain- 

 ing absolute truth. Laplace considered only the solar 

 system, from which he arbitrarily e.xcluded 

 comets ; on the \ast sidereal world he 

 bestowed barely casual attention. Sir 

 William Herschel, on the other hand, 

 occupied himself exclusively with the 

 growth -processes of nebuUf, relegating the 

 details of planetary evolution to a position 

 of secondary importance. Later, the spectro- 

 scope having become available for dis- 

 criminating generic difl'erences among the 

 suns in space, their relative ages, the order 

 of their succession, their mutual affinities, 

 laimed predominant attention. Just now. 



Sinj^le Positive Oischarge on two Coins. Both Coins in .Spherical Connection. 



they had been enclosed and supported in a couple ot 

 circular holes made to fit the coins in a card at the time 

 of exposure. This peculiar feature of the experiment 

 was met with when coins of unequal size and of varying 

 metals were employed, and was also noticed when the 

 glass insulating plate was replaced by an india-rubber 

 pad. 



Modern Cosmogonies. 



VII. Cosmogony in the Twentieth 

 Century. 



By Miss .\gnes Clerkk, F.K.A.S. 

 pROSPECTl\E and retrospectix e inquiries into physical 

 conditions stand \ery much on the same footing. The 

 same degree of uncertainty attaches to results of both 

 kinds ; the same qualifications need to be applied to 

 them ; a similar reserve is understood to accompany our 

 admission of them. The reserve grows more marked 

 as science unfolds to our surprised apprehension the 

 multiplex possibilities of Nature. The time has gone by 

 when " men of light and leading " could draw cheques 

 for unlimited amounts on the bank of public credulity. 

 Not that the balance has diminished, but that it is other- 

 wise employed. Most of us, in these days, have learnt 

 to "look before and after" for ourselves; and we in- 

 stincti\ely mix the pr(j\erbial grain of salt with what is 

 told to us, even on the highest authority. Ideas are on 

 the move ; dim vistas are opening out ; much that lies 

 lieyond the verge of actual experience is seen to be 

 possible, and sedate reasoning may at any moment 

 suffer outrage by fantastic discovery. Hence, dogmatism 

 is at a discount. 



The secular parallax allccting men's views of the 

 universe is nowhere more strongly apparent than in the 



however, the flood of ideas is too high to 

 be restrained within separate channels ; 

 cosniogonists look far afield ; they aim at 

 obtaining a general sur\ey of relations 

 baffling in their complexity. To some ex- 

 tent they have succeeded ; parts are 

 beginning to find their places in a great 

 whole ; links are seen to connect phenomena 

 at first sight seemingly isolated ; on all 

 sides, analogies are springing into view. 

 The unwearied circling of the moon, and its 

 imperturbable face, remind us how a sun 

 may have been born ; the fiash of every 

 meteor suggests the mode by which suns die. 

 The filmy traceries of comets intimate the nature of the 

 force acting in nebulae ; the great cosmic law of 

 spirality is distantly hmted at by the antipodal disturb- 

 ances of the sun. Thus, one set of facts dovetails 

 into the next ; none can be properly considered apart 

 from the rest. 



The limitations of the human mind, nevertheless, 

 require a subdivision of labour. Individual efforts can- 

 not grapple with the whole of the known and the know- 

 able ; and the larger part of both is included in the scope 

 of modern cosmogony. It deals with all that the skies 

 hold, visibly or invisibly ; draws unstintingly on time 

 past and time to come ; concerns itself equally with 

 gradual transformations and sudden catastrophes, with 

 the dissipation and concentration of energy, with the 

 subtle interplay of matter and force, with physical and 

 ultra-physical, chemical and electrical modes of action. 

 But let us consider a little more particularly how things 

 actually stand, so as to collect some definite ideas regard- 

 ing the lines of advance practicable and promising for 

 the immediate future. 



To begin with our domestic circle. The insecure state 

 to which Laplace's scheme has been reduced by the 

 assaults of numerous objectors has found compensation 

 in the development of tidal theory. Much light has 

 thereby been thrown upon planetary pre-history. The 

 relations of planets to the sun, and of satellites to planets, 

 have been rendered comparatively intelligible. Notice- 

 able above all is the discovery thence ensuing of the 

 earth's critical situation, just outside the boundary of the 

 region where planetary rotation was destroyed by sun- 

 raised tides, and with it the prospects of planetary 

 vitality. Moreover, the consequent dubious state of the 

 inchoate terrestrial spheroid accounts for the peculiar 

 mode of birth of the moon, and the distinctively binary 

 character of the earth-moon system; while the variety 

 perceptible in the circumstances of the different planets 

 precludes the employment of any single recipe for their 



