1881. J from the time of Newton. 133 



These views were reiterated in the preface to a second edition 

 of my Chemical and Geological Essays in 1878, and again before 

 the British Association for the Advancement of Science at Dublin 1 , 

 and before the French Academy of Sciences in the same year 2 . 

 They were still f irther developed in an essay on the Chemical and 

 Geological Relations of the Atmosphere, published in the American 

 Journal of Science for May 1880, in which attention was called to 

 the important contribution to the subject by Mr Lockyer in his 

 ingenious and beautiful spectroscopic studies, the results of which 

 are embodied in his " Discussion of the Working Hypothesis that 

 the so-called Elements are Compound Bodies," communicated to 

 the Royal Society, December 12, 1878. It was then remarked 

 that the already noticed "speculation of Lavoisier is really an 

 anticipation of that view to which spectroscopic study has led the 

 chemists of to-day ;" while it was said that the hypothesis put forth 

 by the writer in 1874, "which seeks for a source of the nebulous 

 matter itself, is perhaps a legitimate extension of the nebular 

 hypothesis." 



To shew the connection of the above views with the philosophy 

 of Newton, it now becomes necessary to give some account of the 

 conception of the universal distribution of matter throughout 

 space, both as regards its dynamical relations and its chemical com- 

 position. Passing over the speculations of the Greek physiologists, 

 we come to the controversies on this subject in the seventeenth 

 century, and find, in apparent opposition to the plenum maintained 

 by Descartes and his followers, the teaching of Newton that " the 

 heavens are void of all sensible matter." This statement is how- 

 ever qualified elsewhere by his assertion, that " to make way for 

 the regular and lasting movements of the planets and comets it is 

 necessary to empty the heavens of all matter, except perhaps some 

 very thin vapours, steams and effluvia arising from the atmospheres 

 of the earth, planets and comets, and from such an exceedingly 

 rare etherial medium as we have elsewhere described," etc. (Optics, 

 Book in. Query 28). 



In order to understand fully the views of Newton on this sub- 

 ject it is necessary to compare carefully his various utterances, 

 including the Hypothesis, in 1675, the first edition of the Prin- 

 cipia, in 1687, the second edition, in 1713, and the various editions 

 of the Optics. This work appeared in 1704, the third book, with 

 its appended queries, having, according to its author's preface, been 

 " put together out of scattered papers " subsequent to the publica- 

 tion of the first edition of the Principia. The Latin translation of 



berland, Penn., July 31, 1874; Amer. Chemist. Vol. v. pp. 46—61, and Pop. Science 

 Monthly, vi. p. 420. 



1 Nature, Aug. 29, 1878, Vol. xvm. p. 475. 



5 Comptes Rendus, Sept. 23, 1878; Vol. xxxvm. p. 452. 



VOL. IV. PT. III. 10 



