FOREIGN CORRESPONDENCE. 



433 



besprinkled with this black earth, more efiectually than if sulphur had 

 been emplo3'ed. 



The members of the Societc LnptriaU (T IlortimUxire seemed puzzled 

 not a little as to the nature of this earth; M. Payen, the distinguished 

 chemist, who was present at the meeting, iAsisted that sulphuric acid 

 had been mixed with it, and that this was the cause of its insecticidal 

 and fungus-destroying properties. 11. 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 {S^JerJcise). I have frequently had occa- 

 sion to observe it in Picardy, in certain deposits belonging, I believe, to 

 tlie Subapennine formation, or the terrain cle la Bresse 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-Erute 

 were taken near Ptethel, in the Ardennes.) In the year 1856 the Count 



de la C brought to me a quantity of pj'rites 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 (185G) I had visited, 

 with Professor Koene, of the Prussels University, the large manufac- 

 tory of sulphuric acid belonging to M. Yander Elst, of Prussels. 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 liuppel, in Belgium, whence it is known as la ivjrite de 

 JBooTti. The pyrites of the lignite-deposits mentioned above is almost 

 identical with the latter ; I therefore 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 

 manufactory, 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 m.ade in this 

 paper are found, I have said, in some of the more recent alluvial for- 

 mations, but a compact lignite, which is sometimes used as a combus- 

 tible, exists in many parts of the province ; for instance, at Albert, 

 where it forms long black bands, 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 alter 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 v/ill fix ammonia in the same 

 manner as does sulphate of lime— a proverbially ef&cacious manure. 



Geologie, p. 249. 



t This is often the case in countries where pyrites is common.— T. L. P. 



