GRO 
pratice of his profeffion. But he likewife ftudied under a 
celebrated lithotomift of Amfterdam, from whom he learnt 
that art, and whofe efteem he acquired by the dexterity with 
which he performed the operation, infomuc h that by his will 
were tranflated into Englifh, and the author’s name was 
changed to Greenfield. Eloy. Dict. Hik. 
ROGRAN | 
gon 
inthe Manufaétory, a fort of ftuff, made gona 
ef filk and mohair, being in reality no more than a taffety, 
coarfer and thicker than ordinary. 
GROHNDE, in Geography, a town of Weltphalia, in the 
Feneren of Calenberg on the Wefer, where a toll is paid ; 
nine miles S. of Eom eln. 
GROIN, in natomy. See In el 
GROINE, i in Seka ay. See Cor 
& 
GROINES, or Groynzs, in peony are S peopeeiiann of 
‘wood from the outfides of a pier at the entrance of a nol 
ing 
tchin; 2 “ine is mS of {trong ftakes and wattles of hedge 
lar projections to Sate, from fea-walls or beaks, 
are called hore, jetties, &c. 
G Archite@ure, a {pecies of crofs paffages 
arched ae fo that the hollow of the one arch may cut 
th the folid into the hollow of the other aod and 
at their ert interfe ction. | 
It is evident, that firtt 
ber 
what time they were firft snercdliaea into iethitebee they 
are, howeve remote ; but their antiquity cannot 
tes traced an the es of iii power and grandeur. 
The at the decline of the empire, and 
Rome. In 
temp 
_ the two latter buildin: lings, the groins ove over the great halls {pring 
{fupports, inftead of the maffive piers, 
of refifting the lateral preffure of the arches. 
for the auxiliary fupport of the walls ssichinacky: behind 
buildin. fiit 
which are rot — 
in thefe bui \ coli would not refift the thruft 
of the arches r a fingle ee The exterior walls of 
Dioclefian’s pal at Spa n Dalmatia, and the Gym- 
nafium, at Alexandria-Troas in’ Tots, are alfo vaulted with 
Ather the eitionot the Roman empire, 
to be ufed in ecclefiaftical buildings, and w grandeur 
er decoration was required, they were feldom or never 
palestine they became the moft confpicuous features of all 
fum; -and the pride of th 
en oe decorated with ribs fpringi ae 
anf ee over the = groitd fn 
mc the he prc of the 
af tnt steal 49 ings the celine 
‘cn Cente 
GRO 
remained plain. At laft pillars decorated eh columnar 
mouldings were attached to the walls inftead of fquare 
piers or the wall itfelf, in order to {upport the {pringer 
which were introduced under the groins ; and thefe pil 
being terminated with a ca ital, the abacus of which w 
of the fame form, naturally {uggeited a {mall change in the 
furface of the’ vaultin ‘or the columns now introduced 
ean in we gona epperence a faliant or external 
obtufe till le fides of the obtundin ists terminated in 
two interfeCting ftraight lines in the f ummits 
and formed right <a which were alfo the ultimate angle 
at the diagonal apres Hence the faid feétion of the 
groin above, any pillar being a femi-poly pe approached 
o a femicircle as the number of fpri 
: 
nerated that of pg and founded a fyftem of gant 
altogether upon a new principle, for the conftruétion of 
groins with diffimilar fe€tions, {pringing from a femicircular 
—_— ~ et in Beeorps at the level of the fummits, 
ee would: eafily occur, that any number of equal and fimi+ 
lar ribs, fpringing at the fame angle from a common 
centre in vertical planes, would pb themfelves, pro- 
vided their upper ends were fupported ; and as the hori- 
zontal feétions of the ribs a = dipole, ‘would be in the 
femi-circumference of a circ ommon abutment at 
four angles of a f{quare or oblong; in the fame manner, but 
moft perfeét in the fquare ; then the four abutments for each 
fet of angular {prin ager: wed be quadrants, and thefe qua- 
drants would eel a fpace,and form four convex boundaries 
to that {pace, which, filled in with a flat vault, would key the 
whole together, and keep the quadrantal abutments fta- 
tionary. 
Having thus given a particular and tranfitive idea of 
groins, in order to illuftrate this fhort hiftorical account, it 
will not be improper to define more particularly the various 
fpecies of fimple vaulting, and thence the zener al formation 
of groins, and to fhew how to difcriminate the various 
fpecies, according to the feveral kinds of fimple vaults which 
compofe them ; and laftly, the kereteeg conitruction of 
ees centering and ribbing for plaiteri 
efinitions.—A. fimple vault is an auc concavity ex- 
tended over two parallel ee walls, or over all diame- 
trically oppofite fides of on r wall. 
The een or interior furfice of the vault is called > 
cog 
from, are generalh ftraight li rallel to th of the 
sages: ee y g nes parallel to € axis 
When the vault is fpherical, the circular wall terminates | in 
a level plain at 8 sea from which the vault {prings, and f 
— = —— hemifphere, or a portion of ‘the {phere 
re. pee 
Conic furfaces are feldom employed in vaulting | 3 - 
