Hat, 
Hatching, 
—\~ 
' HA T 
covered. When the crown of the hat is finished in this 
way, the cylindrical part is done by raising up the block 
by its rack and pinion ;,and at last the block is taken to 
pieces to get the hat off. 
For farther information on this subject, see Nollet, 
Art du Chapellier, or Mem, Acad. Par. 1765; Hist. p. 
132; Gerard, Mem. Acad. 1770; Hist. p. 116; Trousier, 
in Rozier’s Journal, vol. xxvii. p. 71; Monge on Felt- 
ing, in the Annales de Chimie, vi. p. 300, or in the Re- 
pertory of Arts, vol. iii. p. 851; Chaussier, in the Jour- 
nal Polytechnique, ov in Nicholson’s Journal, vol. i. p. 
399, or in the Repertory of Aris, vol. x. p. 275; Til- 
stone’s patent for making hats of kids hair, in the Re- 
pertory, Vol. i. p. 1; Dunnage’s patent for water proof 
fits, in imitation of beaver, consisting of silk, mohair, 
cotton, inkle or wool, in the Repertory, vol. iv. p. 302. 
Burns’ patent for a new material for hats, in the Reper- 
tory, vol. ix. p. 167; Dunnage’s patent for ventilating 
the crowns of hats, Id. vol. ix. p. 167 ; Boileau’s patent 
for straw hats, Jd. vol. xi. p. 97 ; Chapman’s patent for 
taking off the fur or wool from skins for hats, Jd. vol. 
vi. p. 374; Messrs Ovey and aca patent for hats, 
Id. vol, xiii. p. 373; Messrs Walker and Alphey’s pa- 
tent for water proof hats, Id. vol. xvi. p. 217; Trans- 
actions of the Society of Arts, vol. i. p. 29, vol, xxiii. p, 
226, vol. xvi. p. 237, and vol. xxv. p. 154; Nicholson’s 
Journal, vol. ii. p. 467, 509, vol. iii. p. 22, 28, 73, vol. 
iv. p. 236 ; Sarrazin, Mecanique propre a carder et me- 
langer les laines et poils servant a la fabrication des cha- 
peaux, in the Archives des Decouvertes, pour 1812, vol. v. 
p. 189; Guichardiere sur un nouveau moyen de fouler 
les chapeaux, in the Archives des Decouvertes, Sc. pour 
1815, p. 198. See also our article ENGLANp, vol. ix. 
p- 11. for an account of the hat manufacture in Eng- 
land. 
HATCHING, is exclusion of the young from the eggs 
of animals, either by the temperature of the circum- 
ambient air, artificial heat, or the incubation of birds. 
Nature has adopted some remarkable distinctions in 
the mode of propagating animals. Some are brought 
to eae in the womb of the mother ; others, origi- 
nally concentrated in eggs, are discharged either in that 
state, where the future concourse of the male is required 
to excite the vital spark, or where the latent embryo 
will be unfolded by the simple application of heat. To 
the first class belongs the oihatina of all quadrupeds ; 
the second includes many of the amphibious tribes, es- 
pecially toads, frogs, and newts; and the third, the 
whole class of birds, numerous fishes and’reptiles, and 
most of the insect, molluscar, and vermicular tribes. 
Hatching and incubation have therefore different mean- 
ings, or the former, which applies to every kind of 
evolution of the nascent being, may be said to include 
the latter. Most animals that produce eggs, leave them 
simply to the care of nature, and certainly never recog~ 
nise their offspring after birth, at least with some excep- 
tions, of which there is a prominent example in the cro- 
codile. But in so far as we can yet ascertain, all birds 
impart their natural heat to their eggs by incubation, 
and watch the developement and subsequent growth of 
their young. Some distant analogy may therefore be 
conceived to subsist between gestation and incubation, 
in the respective period necessary for each according to 
the genera and species of animals. The period of ges- 
tation is generally, perhaps universally, longer in the 
larger viviparous tribes ; and incubation is protracted, in. 
proportion to the size of the bird. One irreconcileable 
difference, however, subsists, in there being no. known. 
method of accelerating the former, while exclusion of 
the young from the egg may be promoted, by aug- 
656 | * ; 
menting the intensity of the temperature. We are yet Hat 
HAT 
unacquainted with the process undergone by the egg of 
the largest of the feathered race, the pray: some as- 
sert that its exclusion is left entirely to the effects of the 
sun ; while others maintain that it is aided by the in- 
cubation.of the female. That of the swan requires ine, 
cubation during 42 days; that of the domestic hen 21 ; 
and that of the linnet 14. But we are told, that the; 
riod is somewhat abridged in the warmer climates ; that 
the egg of the common fowl has been brought out in 13 
days, by the aid of artificial heat ; and that by the di. 
minution or interruption: of the temperature, it has been 
retarded for six weeks. It appears, that the heat of 104° 
of Fahrenheit’s thermometer is required to hatch the 
eggs of all birds, the largest and smallest,.and that the 
surface of the skin of the mother imparts it to that ex« 
tent. Thus nothing more is required for the evolution 
of fecundated eggs, than the simple application of any 
kind of heat. a a 
These facts have been a long time established beyond 
controversy, ‘whence they could not escape the notice 
of the ancients, as they now attract the consideration of 
the most unlearned observers. Instead of abiding by 
the ordinary course which nature has herself committed 
to the parent, mankind, for the sake of deriving more 
profit from their own contrivances, have reso to the 
means of hatching birds by artificial heat. The earliest 
information concerning this process, is probably obtain- 
ed from Aristotle in these words: ‘ Although incubation 
be the common method employed by nature for bringing 
out eggs, it is not exclusive ; for we see that in rt. 
eggs will be hatched of themselves in the earth, if co~ 
vered over and heated by litter,”? And he farther re- 
marks, ‘ that when heated in certain vases wherein 
they are deposited, they hatch of themselves.” Diodo- 
rus Siculus expresses his admiration of the contrivance ; 
and Pliny, who lived a century after Diodorus, re- 
marks, that “ eggs are excluded of themselves quite. 
naturally, and without the aid of incubation by fowls,. 
as in the dunghills of Egypt.” Nevertheless, on com- 
paring this with other passages of his works, it is ob« 
vious that Pliny could not have been ignorant, that 
the application of simple heat was effectual. He and. 
Suetonius relate, that Livia, the wife of Augustus, 
who had before been married to Tiberius Nero, be-« 
came pregnant, and desiring, with all the ardour of a. 
youthful female, to discover of which sex her offspring 
would be, took an egg, that had undergone da in« 
cubation, and kept it warm in her bosom. When obli- 
ged to desist, it was always committed to one of her 
women, that the same invariable heat might be preser~ 
ved. Her object was successful ;. and latter bio~ 
rapher informs us, that ‘from this egg a cock was 
Retshed with a very remarkable crest.” Pliny there« 
fore concludes, ‘ It is probably on such principles, that, 
a method was not. long ago devised, of placing eggs in 
straw heated by a slow fire, a man being occupied in 
turning them at different intervals until their chickens 
were hatched.” In another work of the ancients, the 
Geoponica, there is a whole chapter ascribed to Demoeri- 
tus, treating of “ how it is possible to hatch eggs without. 
the aid of fowls ;” and the principle is analogous to the 
employment of dunghills.. The eggs are to be placed 
in jafs, observing to mark the date of deponie on 
the shell of each, on purpose to ascertain when the 20 
days necessary. for their exclusion shall have elapsed, 
Then the shell is to be broken, and the chickens supplied, 
with food. It is unnecessary to insist farther on the prac- 
tice of the ancients ; but as Herodotus passes over that 
of the Egyptians in silence, some authors have dated its 
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