Weisshorn and the Destruction of the Village of Randa. S7T 
against the danger, or quit their habitations. The most obvious 
mean of defence, is the erection of a high and strong rampart, 
which would resist the influence of the hurricane ; but this ram- 
part, by preventing the circulation of air, might render the vil- 
lage of Randa still more insalubrious, and more subject to cre- 
tinism than it actually is, and it is still doubtful, whether or 
not this wall would shelter them from the storm. 
It might therefore be more advisable to abandon the place, 
and in order that the inhabitants might not be removed far from 
the meadows, it would be necessary to rebuild the village about 
half a league farther up, towards Tesch. The poor inhabi- 
tants, however, cannot adopt either of these methods of safety, 
unless the Government, and the other communes of the canton, 
afford them the necessary assistance. 
Art. X — Historical Account erf Discoveries respecting the 
Double Refraction and Polarisation (f Light. (Continued 
from Vol. III. p. 154.) 
Period II. Containing an Account of Huygeni Theory 
of Double Refraction. Concluded from Vol. iii. p. 154. 
In the section of the crystal which has hitherto been con- 
sidered the unusually refracted ray, lies in the plane which 
passes through the incident ray, and cuts the surface of the 
crystal at right angles. In all other sections, however, the re- 
fracted ray is turned out of this plane. 
In order to explain the cause of this, let ABH, Fig. 1, 
Plate IX. be a perfect rhomb of the spar, so that the obtuse 
angles are bisected by the line EF, and the acute angles by 
Ali perpendicular to EF. 
Let the ray RC be incident in the plane which passes 
through AH, and let C be conceived to be the centre of a 
henii-spheroid, QG M, by which the light is propagated in 
the crystal, and whose section by the plane AEHF forms the 
ellipse QG whose greater diameter Q g' in the line AH, 
will be one of the great diameters of the spheroid ; for since the 
axis of the spheroid is in the plane passing through FEB, to 
