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igneous rocks. It is occasionally amorphous, but more often rudely 
columnar ; it also, though rarely, presents regular columns ; and 
it is sometimes schistose, possessing planes of cleavage as well as of 
regular stratification. 
The scoriaceous basalt is rough and porous, resembling the slag 
of a foundry. Where the bed is thin it is scoriaceous throughout, 
but where it is of a certain thickness only the upper and lower sur- 
faces exhibit this character. ‘Two caverns of considerable magni- 
tude occur immediately to the west of the principal landing-place 
at Funchal, and there are others in the island. 
The vesicular lava or basalt presents through its whole mass a 
porous texture. The large vesicles have been flattened by the gra- 
vity of the lava, and elongated in the direction in which the coulée 
flowed. Where they are numerous and minute, they permit the 
rock to be easily hewn ; and this variety is called cantaria rija, or 
the hard building stone. 
The lapilli, sand, ashes and volcanic bombs, appear to have been 
projected simultaneously, as the bombs were evidently half imbedded 
in the finer materials by the force of their fall, the laminz beneath 
them being bent upwards, and in some instances to a greater height 
on one side than the other, indicating the direction in which the 
bombs fell. 
The pumiceous lapilli are white or light yellow, and rarely ex- 
ceed in size a pigeon’s egg. Beds of pumice, varying in thickness 
from a few inches to several feet, occur either on the surface or in- 
terstratified with the basalt and tufa; and they often contain por- 
tions of heavier volcanic products, as cinders or scorie, dispersed 
without regard to gravitation, proving, Mr. Smith says, that these 
various materials could not have been deposited under the sea, be- 
cause in water they would instantly have separated according to 
their respective weights. The scoriz or cinders also form extensive 
beds. They are generally, reddish, and vary in size according to 
the distance from the orifice of eruption. 
The ashes, both dark and light-coloured, are incoherent, except 
where they are mixed with earthy matter, or apparently fell on a 
heated cone of eruption ; and in these cases they form a scoriaceous 
mass. ‘Tufas and conglomerates compose a large proportion of the 
volcanic rocks of Madeira, and are considered to owe their consist- 
ency to water. Fragments of vegetables are not uncommon in them, 
but Mr, Smith is not aware that they contain any other organic 
remains. Many of these beds have been converted into vegetable 
soils, and it is interesting, the author says, to observe the roots of 
plants still in the attitude in which they grew; and to witness traces 
of the very same phenomena which are now taking place at the sur- 
face, in strata which have been buried for so many ages under solid 
rocks. The remains of plants are chiefly found in the vegetable 
soils, but their roots occasionally occur in the hard rock, and the 
cracks or fissures are in many cases filled with closely-matted masses 
of what was once -roots and fibres, but now consist of carbonate of 
lime. Where the soils have been overflowed with lava, the vege- 
