THE PRODROMUS 261 



form only ; of this last kind there is a great abundance in vari- 

 ous places. 



Regarding the first two classes there cannot be the least 

 doubt that they were at one time actual plants, since the struc- 

 ture of their very bodies compels this view, and the character of 

 the place whence they are dug does not oppose it. They who 

 hold, in opposition, that the earth which had been carried over 

 into houses in process of time changed into wood, cannot affirm 

 this except of the surface of the earth enclosing the wood, 

 where the earth, having become dry in time, and turned to 

 dust, has brought to light the wood enclosed within it. Neither 

 do the metallic filaments found in the pores of the same wood 

 militate against our view, since I myself have drawn from the 

 earth a trunk attesting its plant nature by the knots of its 

 branches and by its bark, whose fissures had been filled with 

 P. 66. mineral matter. Hence, furthermore, it might throw no little 

 light upon the lore of minerals if an investigation were made 

 of the wood, and the place of the wood to determine what they 

 could have contributed to the formation of minerals. Under 

 the name of bitumen come many things which the channels of 

 the fibres and the ashes of the burnt portions prove to be noth- 

 ing but charcoal. 



A greater difficulty is occasioned by the third class of plants, 

 or the forms of plants marked upon stones, since we find forms 

 of this kind in hoar-frost, in the mercury tree,^ in various vola- 

 tile salts, in a white substance ^ soluble in water, which not only 

 forms in glass vessels on their inner surfaces but sometimes 

 rises from the middle of the vessel into the air. But to one 

 who duly weighs all considerations nothing will be found to be 

 inconsistent with the views expressed ; for the forms of plants 

 inscribed on stones are reducible to two classes. Some of 

 these forms are imprinted only on the surface of the clefts, 

 which I would readily acknowledge to have been produced with- 

 out an actual plant, although not without a fluid ; others appear 

 not only on the surface of the clefts but spread their branches 

 everywhither throughout the substance of the stone. Hence it 

 follows that at the time when a plant of the second type was 



1 The metallic crystals produced by mercury in a solution containing silver. 

 ^ Ammonium chloride, sal ammoniac. 



