H Y G 
H Y G 
IIYGE'IA, in mythology, the goddefs of'health, daugh¬ 
ter of AEfculapius, held in great veneration among the an¬ 
cients. Her ftatues repreiented her with a veil, and the 
matrons ufiially confecrated their locks to her. She was 
alio repreiented on monuments like a young woman hold¬ 
ing a lerpent in one hand, and in the other a cup, out of 
which the ferpent fometimes drank. According to fome 
authors, Hygeia is the fame as Minerva, who received 
that name from Pericles, who erected her a ftatue, becaufe 
in a dream fne had told him the means of curing an ar¬ 
chitect, whole allifcance he wanted to build a temple. Pau- 
Janias. 
HYGI'NUS (Caius Julius), an ancient grammarian, 
fiid by Suetonius to have been a native of Spain, though 
fome luppofed him an Alexandrian, and to have been 
brought to Rome after the capture of that city by Julius 
Csefar. He became a freedman of Auguftus; and was 
appointed keeper of the Palatine library. He was very 
intimate with the poet Ovid, and with the confular hilto- 
rian Caius Licinius. Suetonius fays, that Hyginus was a 
ledulous imitator of Cornelius Alexander, a Greek gram¬ 
marian. He wrote lives of illulhious men, referred to by 
A. Gellius and others ; alfo a volume of Examples; and 
a copious Treatife on the Cities of Italy, quoted by Ser- 
vius and Macrobius. A work of his on Genealogies is 
alfo recorded; likewife a Commentary on Virgil, and fe- 
veral other writings. There are come down to our times, 
in his name, only a piece entitled Pocticon AJlr onomicon , de 
Munch & Spliara, ac utriufque Parthim, Declaratione, Lib. IP. 
and a book of mythological fables. The heft edition of 
both in conjunction is contained in Munker’s Mythographi 
La tint, z vols. 8vo.. 
PIYGRAUTIC, adj. [from vy^ot, Gr. moift, and a.v'k oj, 
a pipe.] Belonging to a method of conveying water or 
nioillure in pipes. 
HYGROCIRSOCE'LE, /. [from iy ? og, G r. humid, 
jwcto?, a varix, and y.vhy, a tumour.] A ipecies of hernia, 
from a varicous fpermatic vein, while the l’crotum is at the 
fame time filled with water. 
HYGROCOLLYRHUM, f. [from vy^oc, Gr. humid, 
and a collyrium.] A liquid collyrium, or con- 
lilfing'chiefly of liquids. 
HYGROMETER, or Hy'groscope, f . An inftru- 
nient for meafuring .the degrees of moifture in the air. 
HYGROM'ETRY, f. The fcience of the meafurement 
of the moifture of the air, with the principles on which 
hygrometers are conftructed. Of thefe there are various 
kinds ; for whatever body either fvvells by moifture, or 
{brinks by drynefs, is capable of being formed into an hy¬ 
grometer. Such are woods of moft kinds, particularly 
deal, afh, poplar, &c. Such alfo is catgut, the beard of a 
wild oar, and twitted. cord, See. The molt limple con¬ 
trivances for this purpofe are as follow : 
Stretch a common cord, as reprefented in the annexed 
Engraving at fig. i, ora fiddle-ltring ABD, along a wall, 
palling it over a pulley B; fixing it at one end A, and to 
the other end hanging a weight E, carrying a ftyle or in¬ 
dex F. Againft the fame wall fit a plate of metal HI, 
graduated or divided into any number of equal parts; 
and the hygrometer is complete. For it is matter of con- 
ftant obfervation, that moifture fenfibly fliortetis cords 
and firings; and that, as the moifture evaporates, they 
return to their former length again. The like may be 
faid of a fiddle-ftring; and from hence it happens that 
Inch firings are apt to break in damp weather, if they are 
not llackened by the ferews of the violin. Hence it fol¬ 
lows, that the weight E will afeend when the air is more 
moift, and defeend again when it becomes drier. By 
which means the index F will be carried up and down, 
and, by pointing to the feveral divifions on the fcale, will 
fhow the degrees of moifture or drynefs. 
For a more fenfible and accurate hygrometer, fee fig. 2. 
Strain a whipcord or catgut over feveral pulleys B, C, D, 
63 1 
E, F; and proceed as before for the reft of the conftruCtipn. 
Nor does it matter tvhether the feveral parts of the cord 
be parallel to the horizon', as exprefied in the annexed 
figure, or perpendicular to the feme, or in any other pofi- 
tion ; the advantage of this, over the former method,, be¬ 
ing merely the having a greater length of cord in the fame 
compafs ; for the longer the cord, the greater is the con¬ 
traction and dilatation, and conlequently the degrees of 
Variation of the-index over the fcale, for any given change 
of moifture in the air. 
For another hygrometer, fee fig.- 3. Faften a twilled 
cord, or fiddle-ftring, A. B, by one end at A, fuftaining a 
weight at B, carrying an index C, round a circular fcale 
DE, deferibed on a horizontal board or table. For a cord 
or catgut twills itf’elf as it moiftens, and untwifts again 
as it dries. Hence, upon an increafe or decreafe of the 
humidity of the air, the index will fhow the quantity of 
twifting or uritwifting, and conlequently the increafe or 
decreafe of moifture or drynefs. Thofe Dutch toys 
called weather-houfes K where a finall image of a man, and 
one of a woman, are fixed upon the ends of an index, are 
conftruCled upon this principle. For the index, being 
fuftained by a cord or twilled catgut, turns backwards 
and forwards, bringing out the man in wet weather, and 
the woman in dry. 
For another very fimple hygrometer, fee fig. 4. Faften 
one end of a cord, or catgut, AB, to a hook at A; and 
to the other end a ball D, of about one pound weight; 
upon which draw two concentric circles, and divide them 
into any number of equal parts, for a fcale ; then fit a 
ftyle or index, E C, into a proper fupport at E, fo as the 
extremity C may almoft touch the divifions of the ball. 
Hfre the cord twifting or untwilling, as in . the former 
cafe, will indicate the change of moifture, by the fuccef- 
five application of the divifions of the circular fcale, as 
the ball turns round, to the index C. 
Initead of catgut, Caflebois, a benedi&ine monk at 
Mentz, propofed to make hygrometers of the gut of a- 
filk-worm. When that infeCt is ready to fpin, there are 
found in it two veflels proceeding from the head to the 
ftomach, to which they adhere, and then bend towards 
the back, where they form a great many folds. The part 
of thefe veflels next the llomach is of a cylindrical form, 
and about a line in diameter. Thefe veflels contain a 
gummy fort of matter from which the worm fpins its lilk j 
and, though they are exceedingly tender, means have 
been deviled to extraCt them from the infect, and to pre¬ 
pare them for the above purpofe. When the worm is 
about to fpin, it is thrown into vinegar, and fuffered to 
remain there twenty-four hours ; during which time the 
vinegar is abforbed into the body of the infeCt, and co¬ 
agulates its, juices. The worm being then opened, both 
the veifels, which have now acquired ftrengtlv, are ex¬ 
tracted ; and, on account of their pliability, are capable 
of confiderable extenfion. That they may.not, however, 
become too weak, they are itretched only to the length 
of about fifteen or twenty inches. It is obvious that-they 
muft be kept fufnciently extended till they are completely 
dry. Before they attain to that Hate, they muft be freed, 
by means of the nail of the finger, from a filmy fnbftanee 
which adheres to them. Such a thread will fuftain a. 
weight of fix pounds without breaking, and may be ufed 
for an hygrometer in the fame manner as catgut. 
An hygrometer may be- made of the thin boards of afli 
or fir, by their fwelling or contracting. But this, and 
all the other kinds of this inftrument, above deferibed, 
become in time fenfibly lefs and lefs accurate; till at laft 
they lofe their effeCt entirely, and fuffer no alteration 
from the weather. But the following are much more du¬ 
rable, ferving for many years with tolerable accuracy. 
Take a balance, fig. 5, and to the,tongue or index fix an 
upright piece, D B, at the top of it an arched graduated 
plate A C ; then at the end F hang a weight, and at the- 
A. end. 
