420 THE WORLD MACHINE 



of them are thousands of times the dimensions of the whole 

 solar system. In other words, present-day telescopes, in com- 

 bination with the photographic plate, reveal the objective 

 existence of precisely such masses as the hypothesis had 

 required. Let us clinch the point. 



In some of the older works at least, the ideas of Kant and 

 Laplace are rather scantily dismissed as a mere hypothesis, 

 " interesting if true." We now know that diffused masses of 

 unthinkable extent do exist. The theory of solar energy and 

 of a once molten earth show that such masses must have 

 existed. The especial characteristics of our solar system in- 

 dicated the same thing, and pointed out the probable course 

 of planetary evolution. It would seem as if no further proof 

 were needed ; yet further proof exists. The camera has seemed 

 to reveal that some such a process as Kant and Laplace sup- 

 posed is actually taking place ; not in a single instance nor 

 as an isolated phenomenon, but throughout the whole course of 

 the heavens. 



Herschel's reflector was four feet in diameter. When it was 

 first built it seemed little less than a miracle of ingenuity. It 

 was hardly less a miracle of human patience. A quarter of a 

 century after Herschel's death, and after many unsuccessful 

 experiments, Lord Rosse succeeded in constructing, at Parsons- 

 town in Ireland, a reflecting telescope with a six-foot mirror 

 and nearly sixty feet in length. Its " light grasp " was more 

 than double that of Herschel's. It was with the aid of this 

 beautiful instrument that Lord Rosse disclosed for the first 

 time the existence of spiral nebulae that is, nebulae showing 

 some such a spiral disk that is seen in the little St. Catherine's 

 wheels. Some of his drawings were of exceeding beauty. It 

 was a discovery of the first significance ; but he was an ama- 

 teur and a lord. It is to the discredit of academic astronomy 

 that for a long time Lord Rosse's observations were ignored. 

 Later on, out of an estimated 120,000 nebulae, Professor Keeler 

 could calculate that more than half, possibly nearly all, show 

 this spiral shape. 



It is in the highest degree improbable that this appearance 

 is a mere chance. There seems no escaping the conclusion 

 that these spiral nebulae are in rotation, just as the nebular 

 theory requires. 



There are other appearances which at least suggest a way by 



