Dr. Young’s Lecture on 
H 
wholly borrowed from Newton, Hooke, Huygens, and Male- 
BRANCHE. 
Those who are attached, as they may be with the greatest 
justice, to every doctrine which is stamped with the Newtonian 
approbation, will probably be disposed to bestow on these con- 
siderations so much the more of their attention, as they appear 
to coincide more nearly with Newton’s own opinions. For 
this reason, after having briefly stated each particular position 
of my theory, I shall collect, from Newton’s various writings, 
such passages as seem to be the most favourable to its admis- 
sion ; and, although I shall quote some papers which may be 
thought to have been partly retracted at the publication of the 
optics, yet I shall borrow nothing from them that can be sup- 
posed to militate against his maturer judgment. 
hypothesis 1. 
A luminiferous Ether pervades the Universe , rare and elastic in a 
high degree. 
Passages from Newton. 
“ The hypothesis certainly has a much greater affinity with 
“ his own,” that is, Dr. Hooke’s, “ hypothesis, than he seems 
“ to be aware of ; the vibrations of the ether being as useful and 
“ necessary in this, as in his.” (Phil. Trans. Vol. VII. p. 5087. 
Abr. Vol. I. p. 145. Nov. 16)72.) 
“ To proceed to the hypothesis : first, it is to be supposed 
“ therein, that there is an ethereal medium, much of the same 
i( constitution with air, but far rarer, subtler, and more strongly 
st elastic. — -It is not to be supposed, that this medium is one 
“ uniform matter, but compounded, partly of the main phleg- 
“ matic body of ether, partly of other various ethereal spirits, 
