190 Newton's Letters, Hypothesis and Experiments 



supposed that this medium is one uniform matter, but com- 

 posed partly of the main phlegmatic body of aether, partly of 

 other various aetherial spirits, much after the manner that air 

 is compounded of the phlegmatic body of air intermixed with 

 various vapours and exhalations. For the electric and mag- 

 netic effluvia, and the gravitating principle, seem to argue 

 such variety. Perhaps the whole frame of nature may be no- 

 thing but various contextures of some certain aetherial spirits 

 or vapours, condensed as it were by precipitation, much after 

 the manner that vapours are condensed into water, or exhala- 

 tions into grosser substances, though not as easily condensable, 

 and after condensation wrought into various forms, at first by 

 the immediate hand of the Creator, and ever since by the 

 power of nature, which, by virtue of the command increase 

 and multiply, became a complete imitator of the copy set her 

 by the Protoplast. Thus perhaps may all things be origi- 

 nated from aether. 



At least the electric effluvia seem to instruct us that there 

 is something of an aetherial nature condensed in bodies. I 

 have sometimes laid upon a table a round piece of glass about 

 two inches broad, set in a brass ring, so that the glass might 

 be about one-eighth or one-sixth of an inch from the table, 

 and the air between them inclosed on all sides by the ring, 

 after the manner as if I had whelmed a little sieve upon the 

 table. And then rubbing a pretty while the glass briskly 

 with some rough and raking stuff, till some very little frag- 

 ments of very thin paper laid on the table under the glass 

 began to be attracted and move nimbly to and fro, after I 

 had done rubbing the glass, the papers would continue a pretty 

 while in various motions, sometimes leaping up to the glass 



than in the unexhausted receiver" (Phil. Trans. No. 294. p. 1785). In 

 the 6th Section of the 2nd Book of the Principia, in the scholium to the 

 31st Prop., Newton has given the results of an experiment made by him for 

 the purpose of determining whether the vibration of bodies affords any in- 

 dication of a resisting medium as present in their internal pores, inde- 

 pendent of the resistance which the air makes to the movement of their 

 surfaces. The principal object of this experiment seems to have been, to 

 demonstrate that there exists no resistance of this description equal to that 

 which Descartes's theory of a plenum would require. Newton found the 

 resistance of the internal parts of the box with which he made the expe- 

 riment at least more than 5000 times less than that of its surface. A box, 

 first empty, and then loaded with metal, was swung by a thread of 1 1 feet 

 long; the resistance of the full box compared with that of the empty, by 

 the ratio of the weights to the number of oscillations within measured di- 

 stances, was found to be in a proportion not greater than that of 78 to 

 77. The circumstances of the experiment, however, did not admit of such 

 accuracy as to carry its import beyond the negative object for which it was 

 instituted; and Newton, in the reasons. which he has subsequently assigned 

 for admitting the existence of an aether, made no use of this. 



