On Tropical Miasmata. 33 
of soda had been dissolved. The remark of this able chemist, 
that this mixture had a most insupportable sickening odour, 
much more than that of pure sulphuretted hydrogen, is not to 
be overlooked, because it extremely favours the supposition 
suggested by me, that by the action of vegetable matters on 
sulphates, besides sulphuretted hydrogen, an organic substance 
is produced, which is by far more fatal to animal life than this 
gas. 
«‘ As for the use of the chloride of lime, and the fumigation 
with chlorine, to decompose sulphuretted hydrogen, and thus 
to render it innoxious, it is well known that these means of 
mitigation also effect decompositions of putrefying matters ex- 
haled from the sea-water. Therefore, it is no doubt that these 
means will be, in every respect, very efficacious. 
“Though I am afraid of trespassing too much upon your 
valuable time, yet I cannot conclude this letter without allud- 
ing to a particular decomposition of sulphuretted hydrogen, 
newly investigated by M. Melloni. You will find this very 
interesting Report in a letter of this philosopher to M. Arago, 
published in the Comptes rendus, tom. xi., p. 8352. M. Melloni 
found that a small piece of lighted tinder, or a lighted cigar, 
when placed near one of the fwmaroli, in the Solfatara, near 
Naples, instantly produced a vapour, or a thick white cloud, 
and that this effect reaches to a distance of from five to six 
feet from the lighted substance. M. Melloni caused M. Payen 
to examine into this remarkable phenomenon, and this chemist 
found that sulphuretted hydrogen artificially prepared, and 
mixed with a large quantity of atmospheric air, is affected by 
lighted tinder, or by any lighted substance, in the same man- 
ner as that evolved in the Solfatara. The products of this 
effect are sulphureous acid, water, and a few traces of sulphur. 
Among those circumstances, the ingredients of sulphuretted 
hydrogen are consequently united with atmospheric oxygen, 
and form sulphureous acid and water. M. Payen has further 
detected that iron, and nearly all its natural compounds, as 
iron-glance, titaniferous oxydulated iron, even iron-pyrites, 
and lava, all when heated, act precisely like lighted charcoal. 
“It is evident then, that a lighted cigar, an article fortunate- 
ly common on board all ships, will, in some measure, coun- 
VOL. XXXII. NO, LXIML.—JANUARY 1842, c 
