136 Remarks on Dr. En fees So ak, SEY Oe ae 
andithe-tésolution was accordingly made. © But in doing it, 
two things were confounded which are widely different : the 
sum of the products, and the product of the sums.—It would 
have been better if the compiler had not attempted to de- 
viate from Rutherforth. Supposing only one power, and 
only one resisting force which balance each other through 
the intervention of a series of mechanical powers,—the 
san — be to we: weight simply as the walocity: of the 
is to: the velocity of the powers Cac goby 
rop: 60. The method here given: of Sadie 
pone v velocity of a projectile, gives only yon — . 
which is in-a-direction perpendicular to the horizon 
obtain the whole velocity, this result ought to have sate in- 
creased in the ratio of radius to the cosecant of the angle of 
elevation. But it-would have been altogether preferable to 
omit noticing a method so entirely useless and even de- 
ceptive in practice, : and is substituted in it e by" ud 
ballistic | 
Prop. 68. In the last edition, several Palpable errors 
rected > ec ‘reasoning is still far from ined demonstra- 
tive. The erroneous figure of former editions is also retain- 
per “The circle GNV, instead of GML, should have sneer 
'T for its centre, and GML should have been an hiproie 
img T for its farther focus. 
a a festa Ati is improperly asserted i in this vee 
and t forces differ 
They ssive 
3 and p ercussive forces. © ov the tangent which eneeneltihe 
projectile, and the-subtense which measures the centrifu- 
gal aca be diminished ser aan as — must be before 
we can properly make the attempt to compare them, the 
latter becomes evanescent in eee to ae former. “Phe 
centrifugal is rather a eet tae ——_ — 
than” a part of tel 
POs A When bodies’ aeteieess in a lien bit 
about a — the centripetal and centrifugal forees are 
—— —_— wee in other aalis ae 
es a oc a3 “*8See Rutherforth’s System, sve +: me ee ere 
