16 THE EIGHT HON. LORD KELVIN, G.C.V.O., ON 



the end ; a circumstance that accords well with what is known concerning 

 other parts of the economy of the world. In the continuation of the 

 different species of animals and vegetables that inhabit the earth, we 

 discern neither a beginning nor an end ; in the planetary motions where 

 geometry has carried the eye so far both into the future and the past we 

 discover no mark either of the commencement or the termination of the 

 present order." 



§ 10. Led by Hntton and Playfair, Lyell taught the 

 doctrine of eternity and nniformity in geology ; and to 

 explain plutonic action and underground heat, invented a 

 thermo-electric "perpetual" motion on which, in the year 

 1862, in my paper on the " Secular Cooling of the Earth,"* 

 published in the Transactions of the Royal Society of Edinburgh^ 

 1 commented as follows : — 



" To suppose, as Lyell, adopting the cliemical hypothesis, has done,f 

 that the substances, combining together, may be again separated electro- 

 lytically by thermo-electric currents, due to the heat generated by their 

 combination, and thus the chemical action and its heat continued in an 

 endless cycle, violates the principles of natural philosophy in exactly the 

 same manner, and to the same degree, as to believe that a clock con- 

 structed with a self-winding movement may fulfil the expectations of its 

 ingenious inventor by going for ever," 



It was only by sheer force of reason that geologists have 

 been compelled to think otherwise, and to see that there 

 was a definite beginning, and to look forward to a definite 

 end, of this world as an abode fitted for life. 



§ 11. It is curious that English philosophers and writers- 

 should not have noticed how Newton treated the astro- 

 nomical problem. Playfair, in what 1 have read to you, speaks- 

 of the planetary system as being absolutely eternal, and 

 unchangeable : having had no beginning and showing no- 

 signs of progress towards an end. He assumes also that the 

 sun is to go on shining for ever, and that the earth is to go on 

 revolving round it for ever. He quite overlooked Laplace's 

 nebular theory; and he overlooked Newton's counterblast 

 to the planetary "perpetual moticm." Newton, commenting 

 on his own First Laio of Motion, says, in his terse Latin, 

 Avhich I Avill endeavour to translate, " But the greater bodies 

 of planets and comets moving in spaces less resisting, keep 

 their motions longer." That is a strong counterblast against 

 any idea of eteimity in the planetary system. 



§ 12. I shall now, Avithout further preface, explain, and I 



^ Reprinted in Thomson and Tait, Treatise on Natural Philosophy^ 

 1st and 2nd Editions, Appendix D (g). 



f Principles of Geology, chap, xxxi, ed. 1853. 



