718 I « 
the fame, by the fame change of temperature, whether 
above or below that point. 
“ If heat be taken away from water of 38°, then expan- 
fion is the confequence, and a moderate inclination of the 
particles towards the rhomboidal form; but this only ex¬ 
tends a final! way, whilft the mafs is fubjedt to a tremu¬ 
lous motion, fo as to relieve the obftruflions occaftoned 
by friflion ; by the energy of certain affinities, the new 
form is completed in a moment, and a portion of ice 
formed ; heat is then given out, which retards the fubfe- 
quent formation, till at laft the whole is congealed. This 
is the ordinary procefs of congelation ; 'but, if the mafs 
of water cooled is kept in a ftate of perfeft tranquillity, 
the gradual approach to the rhomboidal form can be car¬ 
ried much farther; the expanfion goes on according to 
the ufual manner, and the flight friftion or adhefion of 
the particles is fufficient to counteract the balance of 
energies in favour of the new formation, till lbme acci¬ 
dental tremor contributes to aajuft the equilibrium. A 
Similar operation is performed when we lay a piece of 
iron on a table, and hold a magnet gradually nearer; the 
proximity of the approach, without contaft, is much 
affifted by guarding againlt any tremulous motion of the 
table. Hence the reft of the phenomena are accounted 
/or.'* 
Though it has been generally fuppofed that the natu¬ 
ral cryftals of ice are liars of fix rays, forming angles of 
6o° with each other, yet this cryftallization of water, as 
it may properly be called, feems to be as much affefled 
by circumilances as that of falts. Hence we find a confi- 
derable difference in the accounts of thofe who have un¬ 
dertaken to defcribe thefe cryftals. M. Mairan informs 
ns, that they are ftars with fix radii; and his opinion is 
confirmed by obferving the figure of froft on glafs. M. 
Rome de Lifle determines the form of the folid cryf- 
tal to be an equilateral octahedron. M. Haflenfratz 
found it to be a prifmatic hexahedron; but M. d’An- 
tic hit upon a method of reconciling thele feemingly 
oppofite opinions. In a violent hail-ftorm, where the 
hailftones were very large, he found they had iharp 
■wedge-like angles of more than half an inch; and in thele 
he fuppofed it impoffible to fee two pyramidal tetrahedra 
joined laterally, and not to conclude that each grain was 
com poled of octahedrons converging to a centre. Some 
had a cavity in the middle; and he law the oppofite ex¬ 
tremities of two oppofite pyramids, which coriftitute the 
octahedron ; he likewife favv the oCtahedron entire united 
in the'middle; all of them were therefore fimilar to the 
cryftals formed upon a thread immerled in a faline folu- 
tion. On thefe principles M. Antic conftruCted an arti¬ 
ficial octahedron refembling one of the largeft hailftones ; 
and found that the angle at the fummit of the pyramid 
was 45 0 , but that of the junction of the two pyramids 
145 0 . It is not, however, eafy to procure regular cryf¬ 
tals in hailftones where the operation is conducted with 
fuch rapidity; in fnow and hoar-froft, where the cryftal- 
lization goes on more flowly, our author is of opinion 
that he fees the rudiments of oCtahedra. 
Ice, as is explained under the article Frost, vol. viii. 
p. 79, forms generally on the furface of water; but this 
too, like the cryftallization, may be varied by an alter¬ 
ation in the circumilances. In Germany, particularly 
the northern parts of that country, it has been obferved 
that there are three kinds of ice. 1. That which forms 
on the furface. 2. Another kind formed in the middle 
of the water, refembling nuclei or fmall hail, 3. The 
ground ice, which is produced at the bottom, elpecially 
where there is any fibrous fubftance to which it may ad¬ 
here. This is full of cells like a wafp’s neft, but lefs re¬ 
gular; and performs many ftrange effeCts in bringing up 
very heavy bodies from the bottom, by means of its in¬ 
feriority in fpecific gravity to the water in which it is 
formed. The ice which forms in the middle of the water 
riles to the top, and there unites into large maffes; but 
the formation both of this and the ground-ice takes place 
only in violent and fudden colds, where the water is dial- 
! E. 
low, and the furface difturbed in fuch a manner that the 
congelation cannot take place. The ground-ice is very 
deftruftive to dykes and other aquatic works. In the 
more temperate European climates thefe kinds of ice are 
not met with. 
Thofe huge maffes of ice which float about upon the 
feas near or within the polar circles, are called by the. 
failors lce-IJlands. Many of thefe fluctuating iflands are 
met with on the coafts of Spitzbergen, to the great dan¬ 
ger of the ffiipping employed in the Greenland fbhery. 
in the mid ft of thole tiemendous maffes navigators have 
been arrefted and frozen to death. In this manner the 
brave fir Hugh Willoughby periftied with all his crew in 
1553; and in the year 1773, lord Mulgrave, after every 
effort which the moft finiflied feaman could make to ac- 
complifn the end of his voyage, was caught in the ice, 
and was near experiencing the fame unhappy fate. The’ 
fcene, diverted of the horror from the expectation of in¬ 
evitable deftruCtion, was the moft beautiful and pic- 
turefque. Two large {hips becalmed in avail bafon, fur- 
rounded on all fides by iflands of various forms; the wea¬ 
ther clear; the fun gilding the circumambient ice, which 
was low, fmooth,' and even; covered with fnow, except¬ 
ing where the pools of water on part of the furface ap¬ 
peared cryftalline with the young ice; the fmall lpace off 
fea they were confined in perfectly fmooth. After fruit- 
leis attempts to force a way through the fields of ice r 
their limits were perpetually contracted by its doling ; 
till at length it befet each veil'd till they became immove- 
ably fixed. The fmooth extent of furface was foon loft; 
the p re flu re of the pieces of ice, by the violence of the 
fwell, caufed them to pack ; fragment rofe upon fra°- 
ment, till they were in many places higher than, the main- 
yard. The movements of the (hips were tremendous and 
involuntary, in conjunction with the fur.rounding ice, ac¬ 
tuated by the currents. The water {hoaled to fourteen: 
fathoms. The grounding of the ice or of the {hips would 
have been equally fatal; the force of the ice might have 
crufiled them to atoms, or have lifted them out of the 
water and overfet them, or have left them fufpended on 
the fummits of the pieces office at a tremendous height, 
expofed to the fury of the winds, or to the rifk of being 
dafhed to pieces by the failure of their frozen dock. An 
attempt was made to cut a paffage through the ice ; after 
a perfeverance worthy of Britons, it proved fruitlefs. 
The commander, at all times mailer of himfelf, directed 
the boats to be made ready to be hauled over the ice, till 
they arrived at navigable water, (a talk alone of leven 
days,) and in them to make their voyage to England.. 
The boats were drawn progreffively three whole^days. 
At length a wind fprung up, the ice leparated fufficiently 
to yield to the preflure of the full-failed {hips, which, af¬ 
ter labouring againft the refilling fields of ice, arrived on 
the 10th of Auguft in the harbour of Smeeringberg, at 
the weft end of Spitzbergen, between it and Hackluvt’s 
Headland. 3 
The forms affumed by the ice in this chilling climate 
are extremely pleafing to even the moft incurious eye. 
The furface of that which is congealed from the lea-water 
(for we mull allow it two origins) is flat and even, hard, 
opake, refembling white fugar, and incapable of beino- 
Hid on, like the Britilh ice. The greater pieces, or field V 
are many leagues in length; the fmaller are the meadows 
of the feals, on which thofe animals at times frolic by 
hundreds. The motion of the fmaller pieces is as rapid 
as the currents; the greater, which are fometimes *two. 
hundred leagues long, and lixty or eighty broad, move 
flow and majeftically ; often fix for a time, immoveable by 
the power of the ocean, and then produce in the horizon 
that bright,white appearance called the blink. The an. 
proximation of two great fields produces a moft finnuiar 
phenomenon ; it forces the fmaller (if the term can be 
applied to pieces of feveral acres fq.uare) out of the wa¬ 
ter, and adds them to their furface ; a lecond and often a 
third fucceeds; fo that the whole forms an aggregate off 
a tremendous height. Thele float in the lea like fo many 
rugged. 
