238 
water, as well as to keep the back up- 
wards when at ref; fo their mufcular ac- 
tions are probably of flow performance, 
and require’ to be of long continuance. 
From thefe and other circumftances 
which Mr. Carlifle enumerates, he infers 
that flownefs of mufcular aéiion, and ex- 
traordinary duration of the contractions, 
are frequently united; and that fuch un- 
ufual phenomena in mulcles are accom- 
panied with a peculiar diftribution of 
the arteries which iupply them: but whe- 
ther the flownefs or the duration be the 
principal end, or whether the equable 
jupoly of blood by a fet of appropriate 
arteries, be the only adaptation convenient 
for the peculiar offices of fuch mufcles, 
are fubjects which Mr. Carlifle does not 
underrake to determine. 
Count RumrForp has prefented to the 
Royal Society an account of a curious 
phenomenon which he, in company with 
Profcf ir Pictet, cf Geneva, obferved on 
the Glaciers of Chamouny. This phe- 
nomenon, which is faid to be very common 
in thole high ecld regions, is thus de- 
feribed : ** At the furtace of a folid mafs 
of ice, of vaft thickne!s and extent, we 
difcovered a pit, perfectly cylindrical, 
about leven inches in diameter, and more 
than four feet aeep, quite full of water: 
the fides were polifhed, and the bottom: 
we'll defined.” 
Frem the guides our philofophical tra- 
vellers l-arnt that thefe cylindrical holes 
are frequently found on the leve! parts of 
the ice; that they are formed during the 
fummer, iscreafing gradually in depth as 
Jong as the hot weather continues; but 
that they are frozen up, and difappear on 
the return of winter. Yhete circumftances 
are thus explained by Count Rumford :— 
*¢ The warm winds which, in fummer, 
blow over the furface ef this column of 
ice-cold water, muft undeubtedly commu- 
nicate ‘ome {mall degree of heat to thofe 
particies of the fluid with which this 
warm aif comes into immediate con'act - 
and the particles of the water at the fur- 
face fo heated being rendered fpecifically 
heavier than they were before, by this 
{mail increafe ot temperatnre, fink flowly 
to the bottom of the pit, where they come 
into contact with the ice, and communi- 
cate to it the heat by which the depth of 
the pit s continually increafed.’” Hence 
cur author proczeds to make fome ob- 
fervations concerning the propagation of 
heat m fluids, in fupport of theories which 
he has advanced on former occafions. 
Mr, HATCHETT, the conftant contri- 
Proceedings of Learned Societies. 
rO& t5 
butor to this fociety, has given an analy 
fis of a triple fulphuret of lead, antimony, 
and copper, which has till lately been re- 
garded as anore of antimony; and which, 
from its fearcity, has been unknown 
to foreign mineralogifts. The fol- 
lowing are the principal characteriftics : 
1. Its f{pecific gravity is 5766 at 56° of 
Fahrenheit. 2. If fuddenly heated upon 
charcoal by the blow-pipe, it crackles 
and {plits ; but when gradually expofed to 
the flame it liquifies, and, upen cooling, 
aflumes a dull metallic grey colour. 3. 
Upon digefting fome of the powdered ore, 
in equal quantiiies of nitric acid and wa. 
ter, with a low heat, a confiderable part 
was diffolved with effervefcence. Some 
fulphur, which floated, was feparated ; 
and the clear liquor, which was of a blue 
vh-green, was decanted from the refiduum - 
at the bottom of the veffel. 4. Muriatic 
acid did not immediately aét upon the 
pulverized ore, but the fo'ution was f{pee- 
dily effected by the <ddition of a few 
drops of nitric acid ; pure julphur was fe- 
parated; and the liquor, being decanted 
in water, yielded a copious precipitate of 
oxide of antimony. ‘The filtrated folu- 
tion, by evaporation, afforded cryftals of 
muriat of lead ; and the lead which re- 
mained in the liquor was feparated by a 
few drops of fulphuric acid. The folu- 
tion was now of a bright green colour, 
and, as before, was found to contain only 
copper, and a minute portion of iron; 
the former was precipitated in the metal- 
lic fate by a plate of zine. - 
Hence it is inferred, that the contituent 
parts of this ore (which was firft defcribed 
by- Mr. Rafhleigh, who poffcifes fome 
perfeét and beautiful fpecimens of it) are 
lead, antimony, copper, and a little iron, 
combined with fulphur; and, from its 
fpecific gravity, colour, fraéture, grain, 
&c. it feems certain that the three firft 
metals exift in the cre, in, or nearly, the 
metallic fate, combined with fulphur, fo 
as to form atriple fulphuret. To afcer- 
tain the proportions, Mr. Hatchett made 
avery accurate avalyfis, and from 200 
grains of ore he found 
Sulphur ° e ° ° 34 grains. 
Oxide of antimony « 63 
Sulphate of lead =. 120.2 
brah 25) 0k. gic eaiee See 
Black oxide of copper 32 
But the metals compofing this triple ful- 
phuret are in the metallic itate, therefcre 
the 63 grains of oxide of antimony muf 
be eftimated at 48.46 grains of metal; 
the 120.2 grains of fulphate of lead are 
equal to 85.24 grains of metal; and the 
-: 32, grains 
