C 440 ] 
than fall fhort of its real magnitude, in thofe cir- 
cumftances, it will be found that every ftroke which 
it receives from them, exceeds not that, which 
an iron fbot, £ of an inch diameter, would give, mov- 
ing only at the rate of 16,16 inches in a year. This 
would be the ftroke if the emiffion were at its max- 
imum. Is it not owing to the extreme minutenefs 
of the fibres of the nerves, that a ftroke, which is 
certainly lefs than the ^L-^th part of this, is not 
fuftained by our organs, without pain ? 
When x~a , the firft of thefe two fluents is the fum of the 
progreflive forces actually imprefled upon the whole hemifphere 
ACB, and the latter is the fum of the forces which would be fo 
imprefled, if all the impinging particles impinged perpendicu- 
larly, and the whole force of each were effedtive. But when x~a 
the firft fluent becomes £ a 4 . And the latter becomes \ a*. 
Whence it is manifeft that the progreflive motion communicated 
to the globe of the earth, by the particles of light, is to the 
force which they would communicate, if the whole force of 
each were eflredtive, in the proportion before alfigned, of one 
to two. 
Received 
