322 On Atmospheric Deposits 
others that of the direction of the wind, at altitudes 
varying from three or four to twenty thousand feet above 
the globe, being constantly, so far as has been explored, 
from either the west, north-westerly, or south-westerly 
points of the compass. It necessarily follows from this, 
that volcanic ashes and dust, if carried up into the lofty 
regions of the atmosphere, would eventually be borne to 
the eastward, and deposited there, unless brought back 
to the west by lower currents from the east: the descent, 
therefore, of dust from the air may be considered an 
evidence of the wind’s direction above, when the pheno¬ 
menon occurs not immediately in the vicinity of a volcanic 
source. 
Several examples, however, of transported dust are 
upon record as having taken place to the west, north, 
and east of Africa, for the source of which the great 
deserts of that country have been assigned. It is my 
persuasion that some of these cases may be referred also 
to volcanic sources rather than to the desert; and as the 
subject may not be uninteresting to the readers of the 
Tasmanian Journal, the following particulars are placed 
before them, not only to register the collected phenomena 
themselves, but to show the evidence by which their 
supposed origin is established.—We will reserve the sup¬ 
posed African cases to be considered last. 
It is assumed in this inquiry, that the winds, as before 
named, at great elevations are westerly : that volcanoes 
pump up their products to those elevations, is easily 
demonstrated. 
Cordier, for instance, calculated that, in 1768, Tene- 
riffe threw scoriae to the height of 3000 feet, i. e . to an 
elevation above the sea of upwards of 18,000 feet. La 
Condamine asserts that Cotopaxi, in one instance, ejected 
ashes to the height of 6000 feet above its crater, or to 
25,000 feet above the sea. Sir W. Hamilton, in his 
