1805.] 
water; and yet, when dry, are little, if 
at ali, affected by it. Lac is foluble in 
the alkalies, and in fome of the acids 3 a 
fact which is ia oppofition to the gene- 
rally received cpinion of chemiis, viz. 
that acids and alkalies do nét aét upon 
refinous bodies. 
The alkaline folutions of refin may be 
found uleful in fome of the arts; for 
many colours, efpecially thofe which are 
metallic, when diffoived in acids, may be 
precipitated, an combined withrefin, by 
adding the former to the alkaline folutions 
of the latter. 
medicine may derive advantages from 
fome of this fertes of alkaline and acid fo- 
lutions of the refinous {ubfances. 
The next ch:mical paper contains 
‘© Obfervations on -Bafalt, with géologi- 
cal Remarks, by Grecory Wart, 
Efq.’’ Thefe are chiefly the refult of the 
following experiment, made on a very 
large fcale, ‘ ? 
One of the common reverberatory fur- 
naces uied in iron-founderjes fer the fufion- 
of pig-iron, was tirongly heated by fre 
and maintained many hous. About leven 
hundred weight of amorphous. bafalt, 
called alfo rowley-rag, was broken into 
fmall pieces, melted, and collected in the 
deeper part. of the furnace, in which, in 
ordinary Operations, the melted iron is 
collected. Itdid not require half the fuel 
“to fufe the bafalt that would have been ne- 
ceflary to melt an equal weight of pig- 
iron, When pertecily mel'ed, it formed 
a liquid glais. The fire was maintained, 
though with gradual diminution, for 
more than fix hours ; the furface of the 
glafs was then covered with heated fand, 
and the furnace was filled with coals, 
which were conlfumed very lowly. After 
eight days, the ma(s-was extracted, from 
a careful examination of which, Mr. Watt 
is led to make a variety of very ingenious 
obfe:vations. Some of thefe illuftrate the 
analogy which exilts hetween the aqueous 
and igneous fo:mations, and fhow, thar 
precifely the {ame order and kind of ar- 
rangement are followed in the generation 
of ttony mafles from water as from fire; 
for the change of ftru€ture, which is the 
moft inexplicable part of the procefs by 
which gisis pafles into fone, is almoft 
exactly imitated in the formation of cal- 
careous fftalactires. 
Having examined the various theories 
on this fubjeé&t, Mr. Watt-obferves, that 
fome of the proceffes defcrined appear to 
yield a provable explanation of fome of the 
peculiarities of bafalt. The general dif- 
pofition of bafalt to divide into globular 
It is probable, alfo, that. 
Proceedings of learned Sacietiess - 143 
maffes, in decompofing, has not been ac- 
counted for. The common effects of 
decompofition are certainly inadequate 5 
for itis common to: fee a large block of 
amorphous bafalt feparate into numerous 
balls, after a few months or years expo- 
fure to the weather; and, rapid as the 
procefs of dccompofition has been in the 
intervening portions, thefe balls refit its 
farther progrefs with uncommon obftinacy. 
This and other phenomena Mr. Watt 
takes pains to illufirate and explain. He 
conceives, that, as a perfeét fimilarity of 
ftructure may exift in the produ&s of 
aqueous and igneous formation, the truth 
of his deduétions are entirely independent 
of either theory ; and that, if ever the pe- 
riod fhould arrive when the origin of bas 
falt fhallbe determined, his inferences may 
be accommodated with equal tacility to 
either mode of agency. He confiders 
moft of the configurations of bafaltic co- 
lumons as fclely attributable to contra&tion, 
which is only a farther extenfion of the 
aggregate force, and muft be regulated 
by the texture, form, and pofition, of the 
mafs. Where the texture of the mafs is 
homogeneous, and its contraétions uni- 
form, its dimenfions may be diminithed 
without lis continuity being defroyed, 
provided its aggregation be fo ftrong as 
to overcome the ~wzs izertia of “the mafs, 
and its adhefion to other fubftances.— 
But, when the refifance is fufficient to 
overcome the aggregation, the mafe will be 
rent by iffures perpendicular to the direc- 
tion in which the greateit refiftance to its 
contraétiin takes place; thercfore, if it 
be an extenfive tabular mafs, it will be . 
divided into prifms by fiffurés perpendi- 
cular to its furfaces. The power of ag- 
gregation would determine thefe prifms to 
be hexagonal, as that form contains the 
greatelt quantity of matter in the leaft fur- 
face of any prifms that can be united, 
without interpofing prifms of other forms. 
But this would require the texture, the 
contragétion, the thicknefs of the mafs, 
and its adhetion to furrounding fubftances, 
to be every. where precitely the fame, 
which are not likely to be found. 
Mr. Watt admits, that though thefe 
confiderations may be fufficient to explain 
the tendency to divifion into prifms, which 
is fo generally extended, and which has’ 
produced many of thofe abortions that 
have been dignified with che name of co- 
Jumns, becaufe they have occurred in layas, 
and in rocks of trap formation, they are 
utterly inadequate to illuftrating the for- 
mation of the more perfect bafaltic prifing, 
They offer no means of accounting for tie 
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