The enquirer. [volume] (Richmond, Va.) 1804-1815, 1810-11-20

y vi ~ hS'tohp'Ntdss il1slnS only the aprIug
ment of these works in IN possession.
wrote to Bishop Madison requesting him to
consult the originals upon The subject, and
in return received the following aiiswer.-
&c haze eonsuited Yince and De La Ian
de 6ut do nor find in either Of their yvorks
any reference 70 The Subject mentioned in
your letter TIE mark of fhe latter is tsvo
large potuncs qnarto FIRST Paris edition.
Indf IF the former IS also in t4vo poiuues
Quarto. a1ith an additional treatise on hrac-
ficat Astronomy. Mr.. Blackburn savs,
that he is assured neither of the syorks
make mention Of fhe Su6jsct. NE haze
nos ne soorks az Gokleo ,n our Li6rary."
Whether The principle have assumed be
Correct or nor, is question which believe
viii not be decided for some time. feel
myself however under the greatest oblga
tions To those Gentlemen who have favored
me with their opinions, and the encomiums
which some have bestowed are certainty
much more than my essay on the diurnal
rotation OF he earth deserved. Among those
can with pleasure mention the name of
Mr. Jefferson, whose &c 4 for the promotion
of mathematical Knowledge is well known
and who regards knowledge of Geometry
as the most important part of the education
of youth.
! With respect to the article ON .sRorA
TON" in the British Encyclopedia. il nav
be proper first to observe tina, this article
was written by the late Professor Robson
OF Edinburgh, man whose Philosophical
and Mathematical talents wers known to
all the learned societies of Europe, md who
was regarded beth in France and Britain
to have few rivals and no superio,. The
theory OF rotation winch he adop.s is entirely
different from that delivered in our oroina
~ school oks, such as Cavailo, Helsham.
Esst,r ii All,
demonstrates thar whatever force. whether
the force OF Gravity or any other force thar
produces TWO motions In "a BODY, a progress
7, sive motion and rotary motion part Of
that force isexpended upon the rotary mo
| ton as ~eiIoss upon the progfessiv. motion.
In RE ordinary Theories Of ifach;nes
! (savs Robison) deducsd entirely from the
principles of Equilibrium, the pressure on
| the points of support Exclusive Of what
proceeds from the weight of the machine
itselD is stated as the same as ii The NOV
ing and resisting forces were applied i'm
| mediately TO these points liz their own iii
rections. But this is in all cases erroneous
| and in cases Of swift motions it is greatw
so We may be convinced of this by a We
ry simple instance.
/" Suppose a line laid over a pulley. and a
! pound weight at one end of it. and ten pounds
/ At the other the pressure Of the axis on It's
support IS eleven pounds, according 10 the
usual rule /; Syhercas We shall find it only
-
| ili.
Tn is Professor Robson demonstrates IN
the most rigid and satisfactory manner In
another place he says" 1t is usual in
courses of experimental Philosophy to Illus.
trate the motions of bodies on inclined Planes
and curved surfaces by experiments with
motions of such rolling Balls are by no
| means Just representations of the motions
they represent The Ball not only goes
down the inclined plane by the action of
Gravity, but it also turns round an axis. -
| Force is necessary Tor producing this rota.
| ton and as .hereis no other source but the
1 weight of the Ball, part of this weight is ex.
| pended on the rotation, and the remainder
! only accelerates it down the Plane'
| From this Theory of Professor Robson.
| it is evident that the most important conse
quences may be obtained for nothing is mare
desirable IN machines which derive their
efficacy from rotary motion, than to apply
the pressnres arising from the power and
the resisting force, in such manner as to
annihilate or diminis, this pressure on the
supports. of tire axis of motion. Proper at
tenien TO this principle will shew wha, NAV
be done. For instance. in all machinery
where the wheel and axe are employed it
! is the general aud prevailing idea, that the
pressure upon the supports Of the axle, is
equal tothe moving power together with the
weight, as also the weight of the wheel and
| axle itself. Nothing is no = yer more diff
ferent from the truth. Even m water
wheels, the pressure upon the support of the
| axle is not equal to the force of the water
and the resistance opposed by tine work for
part OF this force is expended in the rotary
motion of the wheel.
For the same reason If there were no
friction, a carriage Could he easier drawn
without wheels than with wheels. There are
twp other very remarkable properties Of ro
tary and progressive motion.
l5t.>Every point Of body having pro.
srcssive motion and rotary motion about an
axis, as any point in the circumference Of a
Carriage wheel, has also an incn,ient mo
ton about another imaginary axis whose DO
sition is given, and which may be ascertain
ed by the following roportion=--The 70.
tary velocity is to the progressive Veloc rs
the distance ofthe given point from the AK
is OF rotation to its distance from this imaPi
nary axis which has been termed a sponta-
neous axis of conversion.
Cd If body revolves round an axis pas.
sing through its centre of gravity, with the
angular velocity A. Will this axisis CARR
ed round another axis, also passing through
its centre of gravity, with the angular We
locity Is, these two motions combined will
produce motion of every particle of the
body round third avis zinc Il, 49, r,ton.