3-5* tTinfs fir the Formation of 



lubtciTaneaii fires, and which are preceded by or accdmpa* 

 nied with volcanic eruptions ? 



8. Are there any which exhibit indications of the eflefts 

 of water converted into fteani ? 



9. To afcerlain the fimultancous or at lead aftonifliing 

 rapidity of the eflecls of earthquakes at verj' great dittances. 



10. Are there anv inftances thai, durino" the moment of 

 tin earthquake, fome pretty confidcrable trac^l of land, or i. 

 mountain, has been raifed to a great height above its former 

 level, and ha? afterwards rcmainfed in a Hate of elevation? 



11. Are there dry fogs, fuch as that of 1783, which may 

 be confidercd as vapours, that have iffued from the earth by 

 llie a6lion of fliocks or concuffions. 



CHAP. XX. 



Ohfervdtioni to he fiiade on Mines 0/ Metal, Coal, ami Salt. 



I. The hiftorical part: the epoch of the difcovery of a 

 mine ; of its being firlt worked ; the expence and net pro- 

 duce at different periods. If there ever was, or ftill i?, a 

 grant of it, and on what conditions. 



1. A. la regard to the phyfical part, care muft be taken. 

 to examine whether the ore be in veins or ftrata;' that is to 

 fay, whether it interfeclis the Urata of the mountain, or be 

 parallel to them. 



i. In mines which confift of veins, the dimenfions, thick- 

 ncfs, and length of the veins are to be examined ; their in- 

 clination in regard to the horizon, and their dire6lion ii> 

 regard to the cardinal points. The miners call this direc- 

 tion the hours. 



3. The metal it contains; the mineralifingfubftance, and 

 the kind of mineral which thence refulls. 



4. The matrix, or non-metallic foffil, found mixed with 

 the ore. 



5. The nature of the foil at the bottom, or that part of 

 the mountain on which the vein refls ; nature of the cover- 

 ing, or part of the mcuntain immediately above it. 



6. Nature 



I 



