354 
The coal or lignite occurs on the north side of the island, on the 
banks of one of the tributaries of the St. George. Professor John- — 
stone considers it to be the dried relict of an ancient peat bog, and 
its lustre, compactness and rhomboidal fracture to be due to the ac- 
tion of the basalt which overlies it. An analysis gave 
CBT BOMy |e. ik cheer eae e 60°7 
Ey gio genie. eas mney: 5°82 
Oxygen and nitrogen 33°47 
99°99 
and 20°05 per cent. of ash. This is the organic constitution of true 
peat; but no peat exists at present in Madeira, nor as far as Mr. 
Smith is aware, has any been noticed so near the equator. He there- 
fore suggests that this deposit may indicate a former colder climate 
in that latitude. 
The sands of Canical are found near the eastern extremity of the 
island, in a valley w hich extends from the ‘northern to the southern 
shore; and they consist of small particles of basalt and comminuted 
testacea, enclosing vast numbers of land shells as well as calcareous 
incrustations of plants. The shells have been most carefully ex- 
amined by the Rev. Mr. Lowe, and one sixth ascertained to belong 
to species not now found living in the island; the Canical sands 
therefore are assigned by Mr. Smith to the Pleistocene or newest 
tertiary vera. The calcareous incrustations have been considered by 
some observers not to be of vegetable origin, in consequence of the 
general absence of organic structure ; and Dr. Macaulay is of opinion, 
from their consisting of carbonate and phosphate of lime, silica and 
animal matter, ‘that they are of animal origin, and probably belonged 
to the family of Alcyonide. As however they are mere casts, Mr. 
Smith conceives that an analysis cannot throw light on their origin; 
and as all of them bear the most perfect resemblance to trunks or 
branches, and. one of his specimens exhibits impressions externally 
of cellular structure, he has no doubt of their being the calcareous 
casts of plants. 
In one of the small islets adjoining Porto Santo is a bed of fos- 
siliferous limestone, which supplies the kilns of Funchal. The 
fossils consist almost exclusively of casts, but Professor Agassiz 
having been enabled to identify some of them with casts of recent 
species, Mr. Smith infers that the limestone is an extremely modern 
formation, though it has all the characters of primary marble. In 
this case, the volcanic action, Mr. Smith states, was evidently sub- 
marine, as the contact of the basalt and the limestone is so intimate 
that the two rocks never separate when a mass composed partly of 
each is detached by force. The elevation of the islet above the 
level of the sea has not, however, disturbed the horizontal position 
of the beds. 
On the island of Porto Santo the volcanic action was sub- dédok 
as the basalt is scoriaceous on the surface, and rests on volcanic 
brick. In this island there is a sandy deposit similar to that at 
