4 i 4 THE WORLD MACHINE 



A few years after the last essays of Laplace at an explana- 

 tion, twenty years after the earliest of his own, Herschel re- 

 turned to the subject with fresh material for consideration. 

 In two important papers he presented an elaborate theory 

 showing how the " shining fluid " of a broadly diffused nebula 

 might gradually condense under the force of attraction, with 

 the denser portions as nuclei or centres of attraction. The 

 first stage would be a dense nebula or compressed star cluster ; 

 from this would evolve one or more nebulous stars surrounded 

 by an atmosphere. Finally, there would appear a single sun 

 or a series of them. Leaning not upon theory but upon 

 fact, he backed up his conjectures by abundant illustrations 

 from the nebulae and clusters actually observable by the tele- 

 scope. In a word, he adduced evidence to show that the process 

 of sun formation is open to the actual observation of man. 

 It is quite true that the researches of Herschel did not establish 

 the Nebular Hypothesis ; it did not, moreover, attempt to 

 account for planetary formation at all ; but it did lend to the 

 theory an element of objective confirmation which it had 

 hitherto entirely lacked. 



But Herschel, whose genius shines increasingly with the 

 years, and who seems so great to us now, must have seemed 

 otherwise to his contemporaries. His daring and vivid imagina- 

 tion must have excited in them some degree of distrust. Looked 

 at even now, many of the results he attained seem rather the 

 product of an amazing intuition than of a carefully wrought 

 out induction. He had a mind which seemed to leap swiftly 

 forwards to the truth. There are few of his conjectures 

 and their number was extraordinary which have not been 

 more or less completely verified by subsequent research. In 

 his time he must have seemed like a prophet upon Pisgah. 



It was half a century before anything was added to the 

 nebular theory as it was left by Herschel and Laplace. Then 

 came considerations of an utterly different nature indeed, 

 from wholly outside the domain of astronomy. It is curious 

 to reflect that it was of such a nature and such force that it 

 would independently have given rise to some such a theory, had 

 there been nothing else to suggest it. 



The eighteenth century was par excellence the mechanical 

 century. It was the century that perfected the science of 



