1835.] LINES OF VIBRATION. 307 
offended stopped the volcano of Antuco. This silly belief is 
curious, because it shows that experience has taught them to 
observe, that there exists a relation between the suppressed action 
of the volcanos, and the trembling of the ground. It was neces- 
sary to apply the witchcraft to the point where their perception 
of cause and effect failed ; and this was the closing of the volcanic 
vent. This belief is the more singular in this particular instance, 
because, according to Captain Fitz Roy, there is reason to believe 
that Antuco was noways affected. 
The town of Concepcion was built in the usual Spanish 
fashion, with all the streets running at right angles to each other ; 
one set ranging S.W. by W., and the other set N.W. by N. 
The walls in the former direction certainly stood better than 
those in the latter: the greater number of the masses of brick- 
work were thrown down towards the N.E. Both these cir- 
cumstances perfectly agree with the general idea, of the undula- 
tions having come from the S.W.; in which quarter subterranean 
noises were also heard: for it is evident that the walls running 
S.W. and N.E. which presented their ends to the point whence 
the undulations came, would be much less likely to fall than 
those walls which, running N.W. and S.E., must in their whole 
lengths have been at the same instant thrown out of the per- 
pendicular; for the undulations, coming from the S.W., must 
have extended in N.W. and S.E. waves, as they passed under the 
foundations. This may be illustrated by placing books edgeways 
ona carpet, and then, after the manner suggested by Michell, 
imitating the undulations of an earthquake: it will be found that 
they fall with more or less readiness, according as their direction 
more or less nearly coincides with the line of the waves. The 
fissures in the ground generally, though not uniformly, extended 
inaS.E. and N.W. direction ; and therefore corresponded to the 
lines of undulation or of principal flexure. Bearing in mind all 
these circumstances, which so -clearly point to the S.W. as the 
chief focus of disturbance, it is a very interesting fact that the 
island of §. Maria, situated in that quarter, was, during the 
general uplifting of the land, raised to nearly three times the 
height of any other part of the coast. 
The different resistance offered by the walls, according to their 
direction, was well exemplified in the case of the Cathedral. 
