Hale, 
HAL 
The mode of calculation is this: A being the inclina« 
Halstead. tion within the prism, and r the index: Sec. B= 
ion prism, 
Sees = for the incidence ;_S.C=r.S.B, D=C—B.._ As 
S.C  See.'A # S: Dia, 4/3x2y, —y: Fas Rad: T.E, 
2 is the mutual inclination of the planes passing 
through the rays and the axis of the'prism, ane Shen 
Rad: S.F; 2 F is the whole deviation ;, Any yap ate= 
22523 ahr : S. Altitude; S. G, the elevation of the 
Tr < 
plane of the incident ray ; Go 2 E=H the elevation 
239 8.H i: Si 
of the plane of the emergent ray ; 
the depression of the emergent ray. 
Mr Cavendish has suggested, with great apparent 
probability, that the external halo may be produced by 
the refraction of the rectangular termination of the erys- 
tals, rather than by two successive refractions. through; 
the angles of different crystals, which, with the index 
1.31, would produce a deviation: of 45° 44’. If this 
supposition is true, the index cannot be greater than) 
1.31 ; * for 1.82 would give 47° 56’, which is more than 
appears to have ever been assigned. 
The mean of 4 accurate observations is about 45° 50’, 
that of 4 of the best estimations 46°. 
The lateral anthelia may be produced by the rays re- 
fracted after two internal reflections, which will have a 
constant deviation 60° greater than) those: which form’ 
the halo.. These anthelia ought therefore to be about! 
82° from the sun, They are, however, usually represents 
ed as much more distant.” I 
In addition to the works referred to in the course of 
the preceding article, see Zahn Mundi Giconomia. Ly- 
costhenis, Chronicon Prodigiorum. Fritsch On Meteors: 
Philosophical Transactions, 1665—6,i.219. Id. 1669, iv. 
953. Id..1670, v. 1065. Id. 1699, xxi. 107 and.126. Ids 
1700, xxii, 535. Td. 1721, xxxix. 201, 219... Id. 1722, 
xxxii, 89... Id, 1727, xxxv. 257. Id. 1732, xxxvii. 357. 
Id. 1737, x). 50, 54, 59. Fd. 1740, xli. 459. Id. 117425 
xlii. 47, 60, 157. . Id. 1748, xlv. 524. Id. 1749, xlwi. 
203., Id. 1761,,3, 94. Id. 1763, 351. Id. 1770, 129. 
Id. 1784, 59. Id. 1787, 44. Mem. Acad: Parvii. 2086 
Id. x. 47, 152, 168, 275, 401, 454. Jd. 1699, Hist. 82. 
Id..1713; Hist. 67. Fd. 1721, 231. | Id. 1729; Hist. 2. 
Id. 1735, 87, 585. Id. 1743; Hist33. Id. 1745, Hist. 
19. Id, 1753, Hist:'75. Ids 1754, Hist. 82. . Td 1755; 
Hist. 37. Id. 1758, Hist. 23. Id. 1786, 44. Me- 
moires de Berlin, 1734, iv.64. Nov. Comment. Pe- 
trop. vi. 425. Id. viii. 892. Id. x. 875. Weidler, 
De. Parheliis Anni 1736. Irish Transactions; 1787, i. 
23.» Ids 1789, iv. 143: Edinburgh Transactions; iv. 
174. Edinburgh Essays, i. 297. Rozier’s Journal, xi: 
377 3. xxvii S08. “Dr Thomas Young’s NaturalPhilo~ 
sophy, i. 443 ; ii. 308—309 ; and ourarticle Greenbann, 
HALSTEAD, ‘a2 town of England in the county of 
Essex; is agreeably situated on the acclivity of a gra- 
velly eminence, atthe foot of which passes the river 
Colne: Theostreets:of the town are broad and airy, 
but many of the houses are old and inelegant. The! 
church dedicated to St Andrew, is an old-building. It 
consists of a nave, chancel, and’side) aisles;and Has a: 
tower and: spire at the-west end. The spire is of wood, 
and is the third that has been erected, the other two ha- 
* The index of refraction for'ice, according to’ Dr Brewster’s experiments, is 
ments, p. 288. This measure renders Mr Cayendish’s suggestion more probable,“ 
) 618. |) 
H AM - 
ving been destroyed by lightning. The grammar 
odbealoatan Sonxiaioa in the year 1594, by Dame Mary 
Ramsay for 40 poor children of Halstead and Colne- ‘8 
Engaine. The direction of it is vested: in the a 
vernors, &c. of Christ's Hospital, London. The Brides 7 
well isan ancient building... There is:a Greek inscrip~ 
tion on a house’ in the parish, which was from. 
a village near Smyrna, where it had been erected in) 
honour of Crato a musician, about 150 years before 
Christ. Halstead formerly carried on a considerable 
trade in baize and serges, but it has of late much decli- 
ned. In 1802, 1654 were returned as employed in 
manufactures, whereas in 1811 only..11'70 were return< 
ed. In 1811, there were in the town and parish of 
Halstead, -— fy winslow edt, — ee 
‘Inhabited houses... ‘.. « « » 732 
umber se sg Ge Pay lr rer) 
o. employed in agriculture . . 288 
Total population, adinia Serecryhabieta Pr iA, 
See Morant’s History of Essex, and the Beauties of Eng » 
sad uneauiaeseeaohen tat od mre whe diet 
HAM, or Hamm, in Latin a town of 
Wes ia, and capital of the of the same name, 
is ee place where the Asse throws itself 
into the Lippe. Its principal public buildings are its 
parish chana and Colvitisthonsthebint withrahses pro- 
fessors, and it has excellent establishments for the sup- 
port of the poor. Hamwas formerly ene ofthe: Flsaiabs 
atic towns. It has long been celebrated for its excellent - 
hams, which are called hammen in Holland; and for its 
y. Great quantities of linen-are bleached here; 
and itis famous for akind of beer called veut, which 
is sold to'a ‘considerable extent ‘in the neighbourhood. 
Distance from Munster 6 leagues S. E. and from Co-~ 
logne 18 leagues N. E. » sa ant sete 1d 
HAMAH, Epiphania, and the Apamea of Strabo, 
is. a town of Syria, situated ina narrow on the 
banks of the Orontes. It lies between Aleppo and ~ 
Tripoli, and is about 30 leagues east of Tripoli, and 40 
north of Damaseus. It was founded by Seleucus Ni- 
canor, who sup no fewer than 500 elephants in its 
fertile territory ; and is famous for having been the 
place where the Romans, under Aurelius, defeated Ze-~ 
nobia, Queen of Palmyra. Hamah was destroyed in 
1157 by a dreadful earthquake, but was afterwards re« 
built. This town is now celebrated for its water works, 
in which the water is raised from the river by wheels 
$2 feet indiameter. The water fulling into the buckets, 
is elevated to the height of 30 feet, and’ discharged into a 
reservoir, from: which itis: conveyed to the public and 
private baths: The gardens: around) are very agrees 
able and fertile, and) the surrounding» -is well 
adapted for wheat and cotton. The -Maronites built a _ 
chapeb anda tomb heré, from’ which arose a convent 
whichis celebrated in: that part of Syria, There is 
here a castle; Hamah:is the seat of a Jacobite 
bishop; and:a: pacha has the: ment of all the cans 
ton. Population, 4000.: See M: De La Roque’s' Voy- 
age de Syrie. 
HAMB 
URGH is a free imperial city of the duchy 
of Holstem im Lower Saxony, and one’ of the ; 
richest, and’most populous cities in Germany. It is si- 
tuated on the:right’or northern bank of the river Elbe, 
at: the distance of about seventy miles from its discharge 
into the German Ocean.’ East “Long. 9° 56’, North 
1.30%. See Treatise on New Philosophical Instru~ 
