16 ESSAYS snp OBSERVATIONS 
have paffed thro’ rays of light dlowwiide in 
all directions from every fixed ftar in the 
vifible univerfe: And yet, during the whole, 
they have never juitled againft one parti- 
cle of light ; otherways they could not 
have arrived in their true direCtion to our | 
eye. This reflection cannot fail to fug- 
gefta general notion of the rarity and te- 
nuity of light, far furpaffing all the fup- 
pofitions which are ufually made about 
its | 
gs. THe chance which any one body 
has to juftle with others of like magni- 
tude, is leffened in proportion to the bulk 
of the bodies with refpect to the {pace in 
which they move. It muft be therefore 
fuppofed, as we mentioned above, that 
the diftance of the neareft particles, flow- 
ing in the fame and in different lines, muft 
exceed their diameter, not indeed infinite- 
' ly, but a number of times utterly incom> 
parable with all our ordinary numbers, 
in order that a particle may efcape in’ one 
phyfical point of its progrefs: But, that it 
may pafs freely on thro’ the whole diftance 
of the remoteft fixed ftars, it is evident, 
that 
