HartiEy—On Haze, Dry Fog, and Hail. 5d3 
a small quantity of fume had been seen occasionally to escape 
from the shaft. Hail and sleet falling in Dublin came from the 
east or south-east, and therefore lead fume diffused through the air 
might possibly be mixed with any dust travelling with the wind 
upon which moisture would condense and freeze. 
But hail appears to be formed in consequence of very strong 
local currents driving a body of air heavily charged with moisture 
to a great altitude, where the moisture is condensed upon the 
solid particles of dust in the form of ice.1 
On careful consideration, it seems most improbable that the 
actual quantity of lead fume from the particular somrce specified 
could have been sufficient to diffuse through so vast a space at so 
great an elevation as the dark cloud was seen to occupy previous 
to the descent of the hail; and therefore some more extensive and 
copious source of dust of this composition and at a greater distance 
from where it fell must be looked for. Such a district is South 
Wales. In the Vale of Dowlais, in April, 1893, there being an 
easterly wind and a perfectly cloudless sky with bright sunshine 
for several consecutive days, it was noticed that the fume arising 
from the Bessemer works, in operation both there and at Merthyr 
Tydvil, ascended to a great height as a distinct foxy-red cloud be- 
fore it dispersed. Since then the same occurrence has been noticed 
in other districts. It was remarked at the time as continuing in 
this state for some three or four hundred feet above the works ; 
but this was really a minimum estimate made from sketches 
drawn on the spot, and it falls very considerably short of the 
height at which the dust diffused. A thin widely-extended haze 
appeared in the blue sky at what could not have been less than 
4000 or 5000 feet above the Harth, if we may judge from the 
known distance of the observer from the source of the fume and 
the apparent height of the mountains of. known altitudes and at 
similar distances. This haze showed no tendency to settle, but 
wafted slowly to the westward. 
In the Isle of Anglesey, in 1896, on the 23rd of May, the 
atmospheric conditions being precisely similar, that is to say with 
a feeble easterly or south-easterly wind and a cloudless blue sky, 
there appeared, high over Snowdon, commencing at about five 
1“ Les phénoménes de Vatmosphére, ’? p. 274, H. Mohn. Paris, 1884. 
