22 PLEASANT WA YS IN SCIENCE, 



not find evidence against the theory (as those who have 

 advanced the explanation above referred to may be disposed 

 to imagine) in the recognition in the sun's mass of enormotis 

 quantities of one of these elements which, according to their 

 view, ought to be found chiefly in the outer members of the 

 solar system. If those who believe in the nebular hypothesis 

 (generally, that is, for many of the details of the hypothesis 

 as advanced by Laplace are entirely untenable in the present 

 position of physical science) had accepted the attempted 

 explanation of the supposed absence of the non-metallic 

 elements in the sun, they would now find themselves in a 

 somewhat awkward position. They would, in fact, be almost 

 bound logically to reject the nebular hypothesis, seeing that 

 one of the asserted results of the formation of our system, 

 according to that hypothesis, would have been disproved. 

 But so far as I know no supporter of the nebular hypothesis 

 possessing sufficient knowledge of astronomical facts and 

 physical laws to render his opinion of any weight, has ever 

 given in his adhesion to the unsatisfactory explanation 

 referred to. 



The view which I have long entertained respecting the 

 growth of the solar system viz., that it had its origin, not 

 in contraction only or chiefly, but in combined processes of 

 contraction and accretion seems to me to be very strongly 

 confirmed by Dr. Draper's discovery. This would not be 

 the place for a full discussion of the reasons on which this 

 opinion is based. But I may remark that I believe no one who 

 applies the laws of physics, as at present known, to the theory 

 of the simple contraction of a great nebulous mass formerly 

 extending far beyond the orbit of Neptune, till, when planet 

 after planet had been thrown off, the sun was left in his 

 present form and condition in the centre, will fail to perceive 

 enormous difficulties in the hypothesis, or to recognize in 

 Dr. Draper's discovery a difficulty added to those affecting 

 the hypothesis so presented. Has it ever occurred, I often 

 wonder, to those who glibly quote the nebular theory as 

 originally propounded, to inquire how far some of the pro- 



