234 M. Amedee Burat on the Fariations of 



and in which sedimentary formations were at the same time 

 in action. Volcanic soufflards, known under the name of 

 Lagoni, present us with an existing phenomenon analogous 

 to that which w^e are now considering. These soufflards 

 have their outlet into a depression where lagunes have 

 been formed, and they appear to us as centres of meta- 

 morphic alterations, and generations of some particular sub- 

 stances. 



Such are likewise the conclusions of a description of many 

 of these repositories, which we have published and illustrated 

 with plans and sections of mines.* Let us consider the va- 

 riations actually presented by the different substances which 

 constitute the repositories. In the great superficial basins 

 such as those of Moresnet and Dos, we find matters evi- 

 dently stratified by waters ; such are the bole-clays of Mo- 

 resnet, and the sands of Dos, accompanied with pudding- 

 stones and rolled pebbles of white quartz cemented by 

 calamine. In the repository of Mallieue, and in that of the 

 new mountain near Verviers, these sedimentary products, 

 consisting of sand either pure or mingled with clay and mine- 

 rals, such as oxide of iron, calamine, and galena, are found at 

 considerable depths, for example to 30 or 40 yards from the 

 surface, and occupy pretty extensive spaces at these levels. 



From this composition of the superior region of repositories, 

 in minerals principally oxidated, carbonated and silicated, 

 mingled with evident transported products and sediments 

 produced by the action of waters, the first idea of the miners 

 was to conclude that these repositories were simple super- 

 ficial remblais, which had no continuity in depth. These 

 theoretical notions were very general till the great increase 

 in the manufacture of zinc led to the deepening of the works. 



It was then seen that the oxide of iron and calamines of 

 the surface were replaced, as the depth was increased, by an 

 augmenting proportion of pyrites and blende. The galena, 

 which was only in small proportion in the superficial reposi- 

 tories, likewise acquires more importance in the filling up of 



* Etudes sur les gites calaminaires et sur I'industrie du zinc en Belgique. 

 (1846.) 



