a Theory of the Ear flu 341 
£9* In mines which proceed by strata, to observe their 
hature, extent, thickness, inclination, and depth ; their 
interruption by the veins that intersect them ; their alter- 
nate swellings and constrictions, as well as the augmen- 
tation and diminution of their richness, and the signs 
which precede these changes. 
30. Whether it he rare to find, under the form of stra- 
ta, other metallic mines than those of copper, iron, lead, 
calamine, and manganese. 
31. Whether the mines in strata are generally poor 
near the surface of the mountain, and become richer the 
deeper they proceed. 
31. A. Whether mines, where the metal is found in 
lumps or in a mass (stockwerke) ought to be classed 
among those in veins or those in strata ?* 
3&. In coal mines to observe the nature of the coal ; 
more or less compact ; more or less rich in bitumen 5 
more or less mixed with argil or pyrites. 
33. To examine, in the coal, the traces of their ori- 
gin ; whether they have been formed of wood, turf, or 
marine plants. f 
34. To observe whether there are found the remains of 
marine or terrestrial animals. 
35. The progress of the strata : whether it be true 
that they often begin by descending in order to become 
horizontal, and afterwards to re-ascend 5 and that they 
* 31. E. To observe also a third position of the ore, or ore found in the tran- 
sitions (stein-scheidung) ; that is to say, between two kinds of stone of a very 
different nature ; as between argillaceous schist and calcareous stone, between 
the same schist and compound rocks, &c Not to confound this position of ore 
with real veins, nor with metalliferous banks, ore in strata, and the stockwerke, 
Til. 
f 33. A. To distinguish carefully real coal from jet or fossil coal (the braun - 
hohle of the Germans), and from coal earth, as well as from that substance 
known by the Germans under the name of blend-kohle. Til. 
33. B. To examine whether there is not found sometimes in calcareous soil, 
fat, gelatinous coal ; or whether there is never found but dry, friable costl. Til, 
