GYR 
Marchingaares iow el penises 
M fix 
e eaux, > W. of Paris, in France. 
feandon, nea 
Mingranilla, in , Welenals3 in Spain. 
M obberley, in — 
] rer lies N. of ‘Paris, in France. 
Bopsepcaier as 10 miles. N.E. of do. 
Mee hie ae near Paris, do. 
hel kot 
ial 
N kK, Ee in Nottingham mifhire 
Ratchif ‘(Red Hill) 5. W. of Notti ngham. 
Stinchcombe, E. of Be Beaty Glouceiterthire. 
Leicefter 
Triel, near Paris, in France. 
‘Lutbury, S. (Caftle Hay) Staffordthire. 
‘Tuxford (Markham-Moor) Nottinghamfhire. 
Ville-d’ Avray, eight miles W. of Paris, in France. 
Whitehaven, E. Cumberlan 
Witton, ait Northwich, Chethire; 
Tbe mar ly tracts, where gypfum and rock-falt are — 
feem fabjece to circular depreffions, or FunNet-/baped hol- 
lows (fee that article), —_ are noticed by Mr. Jamiefon, 
“* Geognofy,”’ p. 34 and 1 
Gypsum is ufed in the Carre by. way of eatdy for 
wine ; and about M solanpe quantity is tuuned up 
with, the juice of their grap 4 
Gypsum Tymphaicum 1s a name ae given by the ancients to the 
white chalk, which was. by them for the cleanfing 
of clothes, and which makes an exce pla 
without previous bt . See CaLx nativa. 
GY PSY, a name aon to a fet of vagrants. 
TIANS and Gips 
GYRAT ION, Centre of, in Mechanics. When any fyftem 
of bodies, as A pont Plate 1X. Moran ig. X.) 18 ees ts to 
revolve round a centre S by the action of a for 
ce applied at a 
ania in which, if all 
ame force applied at the fame diftance will generate the 
fame angular velocity in the fame time as if the bodies were 
poem at. their : mes na S A, SB, S C: this 
called the centre of gyri 
PX. B. The moving force is here meant to act in the di- 
reCtion of the plane oO the fyftem revolves, and at 
right angles to a line drawn 
appli ied perpendicular to the axis 
Before we can demonftrate the paises a finding the 
centre 6f tion, = is neceflary a few elemen- 
tary i in he doétrine of ae motion. 
nw lia be colleted into a point B (fg: 21) and 
‘ motion - 
r or cement 
See Eayp- 
axis ; it is required to affign what quantity of matter mutt 
be colleG&ted in the point D, fo that D may be accelerated 
ieee cota at the diftance S B, 
tly that the —_ of * and D 
ae Ss abe pase fame i in bekcigter 1 cafes. 
at tee actos 
from: the point at which it is — 
? GYR 
of thefe quantities is defined by the equation 2. be Xa 3 
T'o apply this, it muft be obferved, that although ca 
abfolute force of the weight P aéting upon the pomt D, 
remains Sag the eee yet its effects upon bodied 
motion are in : 
; therefore the 
) will be 
angular motions of B and D are sag and confequently the 
wlbsity of B is to the velocity of D, a D; and fince 
the quantities of matter in B and D are in the dire€t propor. 
tion of the moving uae or of SD: SB, andan inverle 
proportion of the velocities cone or of & D, we 
fhall have the qeamicity of m in B to that contained is 
D, as SD*: S B’, and tees the ee ae 
==s 
Or thus, let « = the quantity of matter ee to be 
collected in D, M the moving force which acts on By m 
that which acts on D, x the velocity of B, ¢ that of D; 
M SD 
thea will a = but — dt eS by the property 
f the lever : 0 s 3D by the nature of angu- 
° e lever: moreover <3 5 3B ¥ = 
: B D 
lar motion, wherefore — = - 
eerie 
ay cole 
in the point. De to which the force is applied. sage 
Cor. ee e moving force is P, and the mals 
moved E ae ase (the inertia of P not being confidered,) 
the force which accelerates D will be that _— of the ac- 
celeration of gravity which is aie ee en 
Pp Px SD 
and intlead of it an a weight B. x 
eB BxEB’ ee 
B x SD 
Cor. 3, et any arg’ of bodies A, B,C, ( ge . 3) 
be put a fixed axis paffing through 5 dy 
the whole 
fyftem will have’ the Jo 
A; B,C, &e. placed : bess ees tap Ay ‘s B, SC, a 
: $ AoE + ep 
thefe being colleéted into the points a, 4, and ¢ ee 
eee ee Se, hee : 
AL x aay Bex SB 5 ee Sx SC. 
<i ee : 
—— = D is that part of 
the. aucideration (of gravity. which is es 
fubftitute the bodies Sop 
