338 On Atmospheric Deposits of Dust and Ashes . 
The conclusion I had come to respecting the Atlantic 
dust is that to which I was led in the case of the dust 
brought by the trade-wind to St. Anne’s, Jamaica; viz. 
that it came to the surface by a wind contrary to that 
which carried it originally from its source. This is 
confirmed by the testimony of a Mr. Burnet, who 
noticed* * an instance of the kind in the month of February, 
1837. His report is this. 
On the 11th of February he was in 4° 20 1 N., 23° W., 
and had a squall from S. E. and heavy rain, the wind 
veering to E. S. E. On the 12th he had the regular 
trade-wind, with a foggy sky and obscured horizon, the 
upper clouds coming from S. W. On the 13th the haze 
increased, and the clouds became denser: red dust then fell 
on his sails. On the 14th the dust increased ; the upper 
clouds still from S. W. On the loth it became clear in 
8° N., 27° W., the nearest African land being 600 miles 
off. He had the same phenomenon in the same place 
in March, 1826. The period of the year, the direction 
of the wind, and the colour of the dust, agree with what I 
experienced in February, 1839. But if the Cape de Verde 
group were not the cause in 1837 or 1826, it may be re¬ 
marked, that as the desert here must be out of the 
question, the dust might have been blown from the lofty 
volcanic mountains at the back of Sierra Leone or the 
Gulf of Guinea ; rising on the latter coast to the height 
meter rose suddenly from 85° to 95°. The heat was horribly op¬ 
pressive, and has so heated the air that there is no moving. 
* * " At half-past two p.m. the hurricane returned ; when 
the whole air was loaded with dust, that made the sun look red. The 
thermometer was in the sun 120°; and at three p.m. at 126°. In 
the shade 100° and 101°, with a very trying E.S.E. wind.” (Notes 
taken during Travels in Africa by the late John Davidson , F.R.S,, 
F.S.A ., 1839.) 
* Nautical Magazine, i. 291. 
