FOREIGN CORRESrONDEXCE. 
433 
besprinkled with this black earth, more effectually than if sulphur had 
been emploj-ed. 
The members of the Socu'tc Impcriale d' HorticuUure seemed puzzled 
not a little as to the nature of this earth ; M. Payen, the distinguished 
chemist, who was present at the meeting, insisted that sulphuric acid 
had been mixed with it, and that this was the cause of its insecticidal 
and fungus-destroying properties. M. Millot-Brute denied having added 
any acid whatever. The next day the earth was sent to me to be 
examined. 
It consists of a friable black lignite, intimately mixed, in its natural 
state, with white iron-pyrites {Spcrhise). I have frequently had occa- 
sion to observe it in Picardy, in certain deposits belonging, I believe, to 
tlie Subapennine formation, or the terrain de laBresse of Beudant,*'' and 
I know that it has been seen in the vicinity of Paris, where it contains 
a considerable quantity of pyrites. (The specimens of M. Millot-Brute 
were taken near llcthel, in the Ardennes.) In the year 1856 the Count 
de la C brought to me a quantity of pyrites extracted from these 
lignite-beds, near Paris, inquiring whether anything could be done 
with them, as they existed in considerable quantities, he said, at the 
very gates of the capital. The pyrites is of that description called 
Sperkise, which, by contact with damp air, rapidly absorbs oxygen and 
becomes sulphate of iron. Earlier in the same year (1856) I had visited, 
with Professor Koene, of the Brussels University, the large manufac- 
tory of sulphuric acid belonging to M. Yandcr Elst, of Brussels. I 
observed that Sperkise was employed in this manufactory instead of 
sulphur.f This Sperkise is obtained from the tertiary clays of Boom, on 
the little river Buppel, in Belgium, whence it is known as la pjrite de 
Boom. The pyrites of the lignite-deposits mentioned above is almost 
identical with the latter ; I tlierefore endeavoured to ascertain if it 
would not be profitable to use the pyrites of the lignite in the manufac- 
ture of sulphuric acid at Paris, but M. de Sussex, director of the Javel 
raanufactorj-, seems convinced that it is cheaper to buy sulphur. This 
may be the case at Paris, but it does not follow that it would be so for 
other localities. 
In Picardy the organic deposits to which allusion is made in this 
paper are found, 1 have said, in some of the more recent alluvial for- 
mations, but a compact lignite, M'hich is sometimes used as a combus- 
tible, exists in many parts of the province ; for instance, at Albert, 
where it forms long black bauds, or seams, in the white chalk, it is 
extracted, and burnt for the ashes which are employed in agriculture 
as manure, &c. In the alluvial beds the lignite is friable and pulveru- 
lent ; it contains a considerable quantity of Sperkise, and is also employed 
by agriculturists, either in its natural state, when it is called Cendres 
noires, or after undergoing spontaneous combustion, or calcination 
( Cendres rouges). It is, doubtless, a valuable manure ; for, as before 
stated, the pyrites it contains is easily transformed, by moisture and air, 
into sulphate of iron ; and sulphate of iron will fix ammonia in the same 
manner as docs sulphate of lime — a proverbially efficacious manure. 
« Geologie, p. 249. 
t This is often the case in coimtries where pyrites is cominon.~T. L. P. 
