332 On Atmospheric Deposits 
there (at Catania, to the south ) it rained ashes all over 
the city, and ten miles at sea it troubled my eyes.”* At 
Malta ashes have also occasionally fallen, which is not 
surprising, when it is considered that both the volcano 
and the island are seen from each other, and all the 
eruptions of the second zone are visible from the latter. 
These facts make it less problematical that the ashes of 
1830 came from Etna, than from the desert. 
It is a singular fact, but there is evidence sufficient to 
prove it, that during the eruptions of both Etna and 
Vesuvius the sirocco wind is frequently contemporaneous, 
rising during the paroxysm; but though the sirocco some¬ 
times, as in July, 1841, brings locusts from Marocco to 
Italy and also to Spain, I think it would be difficult to 
show that African dust comes also. In the case of the 
occasional dust falling with the sirocco, in the Ionian 
Islands, the evidence is always in favour of a transport 
from the volcanoes, and not from the desert. 
Birds and locusts have been occasionally brought to 
Madeira from Marocco by the wind called L’Este ; and 
twice during the winter of 1839 Dr. Macaulay procured 
specimens that way.f But during the L’Este the air, 
instead of being thick with African dust, is said to be re¬ 
markably clear, and the hills present a cloudless aspect. 
This known African wind is, therefore, an evidence 
against dust imported from the desert. L’Este is proba¬ 
bly the result of some eruption to the west of Madeira; 
and. in the case quoted, there was, says Dr. Macaulay, 
an eruption on the south coast of St. Miguel on the 3rd 
December. The wind is drafted thither, perhaps, as the 
sirocco is to Etna or Vesuvius. The locusts prove the 
distance and direction of its course : but if dust is brought 
1000 miles from Africa by the winds, it is singular that 
* True and Exact Relation, p. 9. 
-j* Edin. New Phil. Journ., xxix. 303, 304. 
