330 Hints for the Formation of 
a fermentation, which, acting on grand masses, may dis- 
engage a sufficient heat to produce the effects of a vol- 
cano. 
ip. Or whether, as M. Homme thinks, the fire of vol- 
canoes is kept up by matters accumulated by rivers and 
currents of the sea. 
16 . To search for means of ascertaining the depth of 
the focus of the volcano. 
17. To examine whether, at the moment when an 
eruption begins to take place, there is any remarkable 
change in the tides, currents, springs, and the nearest 
spiracles and volcanoes. 
18. Muddy eruptions : their height, bulk, nature of 
the water they contain ; whether it be saline : nature of 
the earth and stones thrown up ; whether it contains sea 
shells, of what kinds, and in what state. Watery erup- 
tions : the same researches : whether they hold in solu- 
tion earths not usually soluble in water. ^ 
B. Observations to he made at all Times on Volcanoes 
decidedly such . 
19. Nature of the countries and mountains between 
which they are found. 
SO. History of the volcano : its form, height, and ex- 
tent in the most ancient times ; its successive changes 
down to the present moment ; its lateral mouths, and the 
epochs of their formation. 
& 1 . Chronology and enumeration of its different erup- 
tions 5 description of them, and their most remarkable 
characters. 
22. To descend, if possible, into the craters of extin- 
guished volcanoes 5 to measure their depth 5 describe 
* To observe those excavations from which considerable currents of air is* 
sue either periodically or constantly. TiL 
