76 
Proceedings of the Royal Society 
Boyle, with a parallel citation from Mariotte of fourteen years’ later 
date at least. The comparison of the sponges had struck me so 
much, in Mariotte’s work, that I was induced to search for it in 
Boyle, where I felt convinced that I should find it. 
“ This Notion may perhaps he somewhat further explain’d, by 
conceiveing the Air near the Earth to be such a heap of little Bodies, 
lying one upon another, as may be resembled to a Fleece of Wooll. 
For this (to omit other likenesses betwixt them) consists of many 
slender and flexible Hairs ; each of which, may indeed, like a little 
Spring, be easily bent or rouled up; but will also, like a Spring, be 
still endeavouring to stretch itself out again. For though both these 
Haires, and the AEreal Corpuscles to which we liken them, do 
easily yield to externall pressures ; yet each of them (by virtue of 
its structure) is endow’d with a Power or Principle of Selfe- 
Dilatation ; by virtue whereof, though the hairs may by a Mans 
hand be bent and crouded closer together, and into a narrower 
room then suits best with the Nature of the Body, yet, wdiils’t the 
compression lasts, there is in the fleece they composeth an 
endeavour outwards, whereby it continually thrusts against the 
hand that opposeth its Expansion. And upon the removall of the 
external pressure, by opening the hand more or less, the compressed 
Wooll doth, as it were, spontaneously expand or display it self 
towards the recovery of its former more loose and free condition 
till the Fleece hath either regain’d its former Dimensions, or at least, 
approached them as neare as the compressing hand, (perchance not 
quite open’d) will permit. The power of Selfe-Dilafcation is some- 
what more conspicuous in a dry Spunge compress’d, then in a Fleece 
of Wooll. But yet we rather chose to employ the latter, on this 
occasion, because it is not like a Spunge, an intire Body; but a 
number of slender and flexible Bodies, loosely complicated, as the 
Air itself seems to be. ” 
And, a few pages later, he adds : — 
^ .... a Column of Air, of many miles in height, leaning upon 
some springy Corpuscles of Air here below, may have weight 
enough to bend their little springs, and keep them bent : As, (to 
resume our former comparison,) if there were fleeces of Wooll pil’d 
up to a mountainous height, upon one another, the hairs that 
compose the lowermost Locks which support the rest, would, by 
