BOltDA’S MEASUREMENTS. 
from afar were the only sounds that broke the shence of 
nature in these solitary regions. 
Don Cologau’s family has a couiitry-houso nearer ihe 
coast than that I have just mentioned. This house, called 
La Paz, is connected with a circumstance that rendered it 
peculiarly interesting to ns. M. do Borda, whose death we 
deplored, was its inmate during his last visit to the Canary 
Islands. It was in a neighbouring plain that lie measured 
the base, by which he determined the height of the Peak. 
In this geometrical operation the great dracaena ot Orotava 
served as a mark. Should any well-informed traveller at 
some future day undertake a new measurement of the vol- 
cano with more exactness, and by the help of astronomical 
repeating circles, ho ought to measure the base, not near Oro- 
taval, but near Los Silos, at a place called Bante. According 
to M. Broussonnet there is no plain near the Peak of greater 
extent. In herborizing near La Paz we found a great quan- 
tity of Lichen roccella on the basaltic rocks bathed by the 
waters of the sea. The archil of the Canaries is a very 
ancient branch of commerce ; this lichen is however found 
in less abundanco in the island of Teneriffe than in the 
desert islands of Salvage, La Graciosa, and Alegranza, or 
even in Canary and Hierro. We left the port of Orotava 
on the 24th of June. 
To avoid disconnecting the narrative of the excursion to 
the top of the Peak, I have said nothing of the geological 
observations I made on the structure of this colossal moun- 
tain, and on the nature of the volcanic rocks of which it is 
composed. Before we quit the archipelago of the Canaries, 
I shall linger for a moment, and bring into one point ot view 
some facts relating to the physical aspect of those countries. 
Mineralogists who think that the end of the geology of 
volcanoes is the classification of lavas, the examination of 
the crystals they contain, and their description according to 
their external characters, are generally very well satisfied 
when they come back from the mouth of a burning volcano. 
They return loaded with those numerous collections, which arc 
the principal objects of their research. This is not the feel- 
ing of those who, without confounding descriptive minera- 
logy (orvetognosy) with geognosy, endeavour to raise them- 
