For nature is a perpetual circulatory worker, generating fluids out of solids, and solids out of fluids, fixed things out of volatile, & volatile out of fixed, subtle out of gross, & gross out of subtle, Some things to ascend & make the upper terrestrial juices, Rivers and the Atmosphere; & 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, & keep the Planets from receding further from him. And they that will, may also suppose, that this Spirit affords or carries with it thither the solary fuel & material Principle of Light; And that the vast ethereal Spaces between us, & the stars are for a sufficient repository for this food of the Sun and Planets.
Source:
Letter to Oldenburg (7 Dec 1675). In H. W. Turnbull (ed.), The Correspondence of Isaac Newton, 1661-1675 (1959), Vol. 1, 366.
Contributed by:
Meenakshi 
