134 Dr Hunt, Celestial Chemistry [Nov. 28, 



the Optics, by Dr Clarke, which was published in 1706, and the 

 second English edition, in 1718, contain successive additions to 

 these queries, which are indicated in the notes to Horsley's edition 

 of the works of Newton, and are important in this connection. 

 From a collation of all these, we learn how the conceptions of 

 the Hypothesis took shape, were re-inforced, and in great part 

 incorporated in the Principia. 



In the Hypothesis he imagines " an etherial medium much of 

 the same constitution with air, but far rarer, subtler, and more 

 elastic." " But it is not to be supposed that this medium is one 

 uniform matter, but composed partly of the main phlegmatic body 

 of ether, partly of other various etherial spirits, much after the 

 manner that air is compounded of the phlegmatic body of air, 

 intermixed with various vapours and exhalations." Newton far- 

 ther suggests in his Hypothesis that this complex spirit or ether, 

 which, by its elasticity, is extended throughout all space, is in con- 

 tinual movement and interchange. "For nature is a perpetual 

 circulatory worker, generating fluids out of solids, and solids out of 

 fluids, fixed things out of volatile, and volatile out of fixed, subtile 

 out of gross, and gross out of subtile ; some things to ascend and 

 make the upper terrestrial juices, rivers, and the atmosphere, and 

 by consequence others to descend for a requital to the former. And 

 as the earth, so perhaps may the sun imbibe this spirit copiously, 

 to conserve his shining and keep the planets from receding farther 

 from him ; and they that will may also suppose that this spirit 

 affords or carries with it thither the solary fuel and material 

 principle of life, and that the vast etherial spaces between us and 

 the stars are for a sufficient repository for this food of the sun and 

 planets." 



The language of this last sentence, in which his late biographer, 

 Sir David Brewster, regards Newton as " amusing himself with the 

 extravagance of his speculations," at which "we may be allowed to 

 smile 1 ," was not apparently regarded as unreasonable by its author 

 when, more than ten years later, he quotes it in the postscript of 

 his letter to Halley, dated Cambridge, June 20, 1686. The views 

 therein contained, with the single exception of the suggestion re- 

 garding gravitation, have not wanted advocates in our own time, 

 and many of them were embodied in the Principia, which Newton 

 was then engaged in writing. 



But this was not all: Newton saw in the cosmic circulation and 

 the mutual convertibility of rare and dense forms of matter a uni- 

 versal law, and rising to a still bolder conception, which completes 

 his Hypothesis of the Universe, adds : " Perhaps the whole frame 

 of nature may be nothing but various contextures of some certain 

 etherial spirits or vapours, condensed, as it were, by precipitation, 



1 Brewster's Memoirs of Newton, Vol. i. pp. 121 and 404. 



