NEWTON TO BOYLE

Cambridge, 28 February 1678/9

Honoured Sir,

I have so long deferred to send you my thoughts about the physical qualities we spoke of, that did I not esteem myself obliged by promise, I think I should be ashamed to send them at all. The truth is, my notions about things of this kind are so indigested, that I am not well satisfied myself in them; and what I am not satisfied in, I can scarce esteem fit to be communicated to others; especially in natural philosophy, where there is no end of fancying. But because I am indebted to you, and yesterday met with a friend, Mr. Maulyverer, who told me he was going to London, and intended to give you the trouble of a visit, I could not forbear to take the opportunity of conveying this to you by him.

1. It being only an explication of qualities, which you desire of me, I shall set down my apprehensions in the form of suppositions, as follows. And first, I suppose, that there is diffused through all places an aethereal substance, capable of contraction and dilatation [i.e. dilation], strongly elastic, and in a word much like air in all respects, but far more subtle.

2. I suppose this aether pervades all gross bodies, but yet so as to land rarer in their pores than in free spaces, and so much the rarer, as their pores are less.