320 Of Vegetation . 
of air, which has a wonderful property of 
ftrongly attrading in a fixt ftate, or of re- 
pelling in an elaftick ftate, with a power 
which is fuperior to vaft compreffing forces * 
and it is by the infinite combinations, adion 
and re-adion of thefe principles, that all 
the operations in animal and vegetable 
bodies are effeded. 
Thefe adive aereal particles are very fer- 
viceable in carrying on the work of vegeta- 
tion to its perfection and maturity. Not 
only in helping by their elafticity todiftend 
eachdudile part, but alfo by enlivening and 
invigorating their fap, where mixing with 
the other mutually attrading principles they 
are by gentle heat and motion fet at liberty 
to afllmilate into the nourifhment of the 
refpedive parts : “ The foft and moift nou- 
“ rifhmenteafily changing its texture by gen- 
C€ tie heat and motion, which congregates 
“ homogeneal bodies, and feparates hete- 
rogeneal ones.” Newtons Opticks , qu. 
31. The fum of the attrading power of 
thefe mutually ading and re-ading principles 
being, while in this nutritive ftate, fuperior 
to the fum of their repelling power, where- 
by the work of nutrition is gradually advan- 
ced by the ne^er and nearer union of thefe 
4. prin- 
