8 .A S A 
ferves, that the bending pillars of Staffa differ confidera¬ 
bly from thofe of the Giant’s Caufeway. In Staffa they 
lie down on their Tides, each forming the fegment of a cir. 
cle ; and, in one place, a fmall mafs of them very much 
refembles the ribs of a fhip. Thofe of the Giant’s Caufe¬ 
way which lie Taw, ran along the face of a high cliff, bent 
ftrangely in the middle, as if unable, at their firft forma¬ 
tion, while in a foft ftate, to fupport the mafs of incum¬ 
bent earth. 
The rocks of the Cyclops, in the neighbourhood of Et¬ 
na, exhibit very magnificent bafaltic pillars, which we 
have reprefented in the annexed Plate. Near thefe rocks 
is an ifland, one half of which is comported of lava, on a 
bafe of balaltes; above which there is a cruft of pozzo- 
lana, combined with a certain white calcareous matter, 
which is hard and compaft ; and which, as it is compofed 
by the aftion of the air, appears like a piece of knotty 
porous wood. The ifland was formerly inhabited; and 
there ftill remains a flight of fteps leading from the fhore 
to the ruins of fome houfes which appear to have been 
hewn in the rock. Thefe bafaltic columns are of various 
fizes and forms; fome fquare, others hexagonal, heptago- 
rial, or oftogonal. One half of this rock is compofed of 
perpendicular columns; the other of another fpecies of 
bafaltes difpofed in inclined, and almoft rectilinear, layers. 
Thefe are in contaft with the columns, and are asclofely 
eonncfted with them as they are with one another. The 
layers are longer at the bale than towards the top of the 
rock. It is farther to be remarked, that mod of thefe 
layers ate fubdivided as they rife upwards; fo that, to¬ 
wards thefe upper extremities, one layer p relents to the 
eye fometimes one, fometimes two, and lb me times three, 
divifions. The fragments of bafaltes taken off from thefe 
layers are of a rhomboidal figure, becaufe the layers break 
obliquely. Thefe layers, though inclined towards the 
bafe, become almoft perpendicular towards the upper part 
of the rock, where they appear united in a point, and over¬ 
top moft of tire vifible and elevated parts of the prifmatic 
columns. Thefe columns terminate in fuch a manner as 
to form a kind of ftaircafe. They appear even to rife un¬ 
der a fpecies of clay with which they are covered at one 
extremity, till they re-unite themfelves with the point 
which is formed by the moft elevated parts of the layers 
of bafaltes befide them. 
The promontory of Cartel d’laci, which terminates the 
balls of Etna, is almoft entirely compofed of bafaltes, but 
of a kind very different from the former. It confifts of a 
great number of cylinders from the diameter of fix inch¬ 
es to that of twenty feet. Some of thefe are folid, others 
hollow like cannon ; fome extended in layers, others ftrni- 
lar to carrots of tobacco confiding of a number of pieces 
fqueezed together. Some of thefe cylinders are ftraight, 
others curved into a variety of forms. Some look like 
globes inclofed in the rocks; and in the fraftures of thefe 
globes we perceive the ftrataof which they are compofed. 
Thefe are delineated at the foot of the annexed Plate. 
The little mounts into which it appears to be colleiSted, are 
fometimes only one French foot in diameter, fometimes 
fix. They are compofed of fmall prifms or needles, or of 
cubic trapezoids, and conlift of a matter diftinguifhed by 
the name of dirty,lava. It is made up of pozzolana, con- 
folidated by a certain liquid, which, while it has commu¬ 
nicated folidity to the pozzolana, has at the fame time buf¬ 
fered that fubftance to fhrink confiderably, in fuch a man¬ 
ner as to leave large chinks between the pieces of bafaltes, 
which are thus formed by the operation of the liquid on 
the pozzolana. It appears alfo to have infinuated itl'elf 
into the clay with which the promontory is covered ; which 
lias become hard in its turn, and which has alfo fpli.t into 
chinks that appear to contain a kind of hard matter. Thefe 
del'criptions and figures will ferve to give a pretty correct 
idea of the appearance of the bafaltes, which is general¬ 
ly accounted a kind of marble. Wallerius calls it a fpe¬ 
cies of the corneous or horn-rock; and Cronftedt enume¬ 
rates it among thofe fubftances which he calls garnet earths , 
Vol.II. No. 102, 
L T E S. 
The largeft block of this ftone that ever was feen, was 
placed, according to Pliny, by Vefpafian in the Temple of 
Peace. It reprefented the figure of Nilus, with fixteen 
children playing about it, denoting as many cubits of the 
rife of the river. The ftatue of Memnon in the Temple of 
Sera pis at Thebes, which founded at the riling of the fun, 
was alfo made pf the fame material, if we may believe 
this author. Moft of the Egyptian figures are likewife 
made of bafaltes. Some of the ancients call it lapis Lydius„ 
from Lydia, where it was formerly found in great abun¬ 
dance. The moderns denominate it the touc/i^flone, as be¬ 
ing ufed for the trial of gold and filver. 
It has been a matter of controverfy among many mine- 
ralogifts, whether the bafaltes has been formed by cryftaL 
lization from water,- or from volcanic fire. In fupport of 
the volcanic origin of the bafaltes, it has been argued : i. 
That it agrees almoft entirely with lava in its elementary 
principles, in its grain, the fpecies of the foreign bodies 
it includes, and all the diverfities of its texture. 2. The 
iron of the bafaltes is found to be in a metallic ftate, ca¬ 
pable of afting on the magnetieal needle, which is alfo 
the cafe with that found in compaft lava. 3. The bafal¬ 
tes is fufible pcrfc\ a property which it has in common 
with lavas. 4. The bafaltes is a foreign lubftance fuper- 
induced on the original limeftone-foil of the country, in a 
ftate of foftnefs capable of allowing the flints to penetrate 
confiderably within its lower furface. 5. Thofe extenlive 
beds of red ochre which abound among our bafaltes are 
fuppofed to be an iron earth reduced to this ftate by the 
powerful aftion of heat; for fuch a change may be pro¬ 
duced on iron in our common furnaces, provided there be 
a fufficient afflux of frefh air; and the bafaltes it felt", on 
fuch circumflances, is eafily reducible to an impure ochre. 
This is alfo found to take place in the living volcanoes, 
particularly within their craters ; and is therefore hippo- 
fed to afford a prefumptive argument of the aft ion of fire 
in the neighbourhood of balaltes. 6. Though zeolite is 
not yet proved to be the aftual produftion of a volcano, 
yet its prefence is always fuppofed to give countenance to 
this hypothefis; becaufe zeolite is found in countries where 
the aftion of fubterraneous fire is full vifible, and where 
there is reafon to believe that the whole foil has been ra¬ 
vaged by that principle. Thus it abounds in Iceland, 
where the flames of Hecla yet continue to blaze; and in 
the ille of Bourbon, where there is ftill a volcano in force. 
It is therefore fuppofed to arife from the decompofition of 
the produfts of a volcano, where the fires have been long 
extinft. 7. Cryftals of fchorl appear in great plenty a- 
mong many kinds of our bafaltes ; and thefe, though not 
abfolutely limited to volcanic countries, yet, being found 
i-n great abundance among the Italian lavas, in circum- 
liances exaftly correfponding to thofe of our bafaltes, are 
thought to fupplya good probable argument in the pre- 
fierit cafe. 8. The peperino ftone is thought to be un¬ 
doubtedly of a volcanic origin. It has frequently the 
burnt and fpo'ngy appearance of many of the volcanic pro¬ 
dufts ; and that of the Giant’s Caufeway agrees exaftly 
with the peperino of Iceland and Bourbon. 9. Puzzolane 
earth is met with among the bafaltas of France ; and there 
is very little reafon to doubt that our bafaltes, if pulve- 
rifed, would agree with it in every refpeft ; that is, it 
would produce a fine fharp powder, containing the fame 
elementary parts, and probably agreeingwith it in its va¬ 
luable ufes as a cement. This eartli is alfo found in the 
Canary iflands, which are thought to have other marks of 
fire; it is met with in all the volcanifed parts of Italy, 
and is never found excepting where there are other evi¬ 
dent marks of fire. 10. Pumice ftone is univerfally al¬ 
lowed to be produced by fire, and indeed bears the refem- 
blance of a cinder fo obviouily, that one mud be inftant- 
ly convinced of its original. This is alfo found among the 
bafaltes of Ireland. 11. There are three living volcanoes,- 
within whofe neighbourhood, the bafaltes and moft of its 
ufual attendant foffils have been obferved, viz. Etna in 
Sicily, Hecla in Iceland, and the ifland of Bourbon on the 
9 K co^fi 
