1882.] 
Correspondence . 
749 
THE ‘ SULPHUR THEORY” OF FOGS. 
To he Editor of the Journal of Science. 
Sir, — The og-season having again come round, and found us 
practically as open to its attacks as we were ten years ago, you 
will perhaps permit me to ask whether the fashionable theory of 
its origin is well-founded ? If we make careful observations we 
find that fogs have very well-marked local boundaries which are 
often found to be the same year by year. Can it be for a moment 
supposed that these boundaries mark out constant differences in 
the chemical composition of the air, sulphur being present on 
one side of the line and absent on the other ? 
Eight years ago I remember a fog which overspread all London , 
being as opaque in Holloway, Camden Town, Westminster, and 
Hackney, as in the City, I happened to be going in the after- 
noon to Chingford. When past Hale End the train suddenly 
dashed out into clear air and bright sunshine. On looking back, 
either to the right or left hand, the fog lay sharply cut off like a 
fleecy wall, and seemed to be constantly recruited by vapour 
which rose up like smoke from among the clods of the ploughed 
fields. Is it likely that sulphur was theacting cause of fog in a 
neighbourhood so free from houses as the country between Hale 
End and Chingford ? Sulphur fumes cannot have been brought 
by the wind from London, for what little current was perceptible 
in the air was in the opposite direction. Had such fumes been 
brought, would not their influence have gradually faded away 
instead of being abruptly cut off? 
As a somewhat similar phenomenon to the abrupt termination 
of fogs I may mention abrupt breaks in the clouds, which, though 
not constant, are very frequently observed in some particular 
quarter of the heavens. Years ago, when living at Gorton, a 
village south-east of Manchester, I very often noticed that when 
the sky was clouded overhead and in all other directions, there 
was low down, near the horizon, bright sky visible to the south- 
west, as if it might be over the estuary of the Dee. Such breaks 
seemed independent of the direction of the wind, and remained 
without change for hours. — I am, &c., 
Skv-gazer. 
