THE PRODROMUS 229 



jects, we rightly surmise that this matter was swept thither by 

 the flooding of a river, or the inflowing of a torrent. 



5. If in a certain stratum pieces of charcoal, ashes, pumice- 

 stone, bitumen, 1 and calcined matter appear, it is certain that a 



P. 29. fire occurred in the neighborhood of the fluid ; the more so if 

 the entire stratum is composed throughout of ash and charcoal, 

 such as I have seen outside the city of Rome, where the mate- 

 rial for burnt bricks is dug. 



6. If the matter of all the strata in the same place be the 

 same, it is certain that that fluid did not take in fluids of a dif- 

 ferent character flowing in from different places at different times. 



7. If in the same place the matter of the strata be different, 

 either fluids of a different kind streamed in thither from differ- 

 ent places at different times (whether a change of winds or an 

 unusually violent downpour of rains in certain localities be the 

 cause) or the matter in the same sediment was of varying grav- 

 ity, so that first the heavier particles, then the lighter, sought 

 the bottom. And a succession of storms might have given rise 

 to this diversity, especially in places where a like diversity of 

 soils is seen. 



8. If within certain earthy strata stony beds are found, it is 

 certain either that a spring of petrifying waters existed in the 

 neighborhood of that place, or that occasionally eruptions of sub- 

 terranean vapors occurred, or that the fluid, leaving the sediment 

 which had been deposited, again returned when the upper crust 

 had become hardened by the sun's heat. 



Concerning the position of strata, the following can be con- 

 sidered as certain : 



I. At the time when a given stratum was being formed, there 

 was beneath it another substance which prevented the further 

 P. 30. descent of the comminuted matter ; and so at the time when the 

 lowest stratum was being formed either another solid substance 

 was beneath it, or if some fluid existed there, then it was not 

 only of a different character from the upper fluid, but also 

 heavier than the solid sediment ^ of the upper fluid. 



1 The inclusion of bitumen in the list indicates that Steno was ignorant of its true nature 

 as an organic compound. 



2 sedimenta, Florentine edition, is an error for sedimento. 



