(382 Leiter from the Chevalier de Martius to the Editor. 
25. Products of the Combustion of certain Coal Strata.—- 
In the. neighbourhood of Aubin ( Aveyron) there exist certain 
coal strata, some of which are worked, and others are burn-. 
ing. having been on fire for thirty or forty years. ‘At has- 
been remarked as singular, that no muriatic acid, or am- 
monia, occurs in the products of this combustion. Much 
sulphurous acid escapes, and various portions of sublimed 
sulphur, and acid aluminous efflorescences have’ been col- 
— lected; but on chemically examining these and other pro- 
_ ducts obtained, neither muriatic acid nor ammonia have 
been observed. The coal nevertheless contains an abun- 
dance of azote, and on distillation affords warbeoay of am- 
monia. Bs | 
26. . Letier from the Chevalier de Martius. to the Editor. 
REMARK. 
The following letter was received, just as the last pages 
of this number were going to the press. As the Editor 
is very desirous to promote the laudable wishes of his cor- 
respondent, he publishes the entire letter with the bai 
tion of a few passages. ; 
This course appears to be proper, as. the communica- 
tion relates to the interests of science at large.—Ep. - 
Munich, 13th Feb. 1824. 
Si— ae 
Beins a diligent reader of your excellent American 
Journal, | cannot but desire to establish an intercourse 
between us, which, | hope, will prove useful both for you 
and me. My principal study is Botany, but | am also 
fond of Geology, and wish to further these two sciences 
by their mutual influence. Ina tour through a great part 
of Brazil, performed in the years 1817—1820, | had often 
occasion to explore the relation of geological facts with 
others interesting to the Botanist. | beg your permission, 
Sir, to send you two short dissertations on such objects, 
which I consider only as precursors of larger communica- 
tions. My friend and companion, Dr. de Spix and | pub- 
