tion and if implemented under geologically plausible condi- 
tions, factors and constraints of importance to the natural 
process might be recognized and characterized. Described in 
this section is a procedure which offers some promise in this 
direction. 
Earlier Work 
Around 1520, the alchemist, Basil Valentine, reputedly de- 
veloped a procedure whereby wood could be artificially pet- 
rified (Vail, 1928). The silicifying agent was said to be a fluid 
formed from powdered silica and ‘sal tartari’, the latter, pre- 
sumably, being the ‘subtartrate of potash’ derived from grapes. 
In the same century, Kentmann (1518-1568) wrote of having 
prepared a ‘lapides igne liquescentes’ from alder wood. Meyer 
(1791) accredits Kentmann with the following statement: 
‘*When one brews beer. alder wood is simmered in the pot until 
the hops are done. Afterwards, one buries the wood for three 
years in fresh sand or gravel in a cellar, afterwhich, it turns 
hard, making the best whet- or flintstone.’’ It might be noted 
here that beer itself is essentially saturated with respect to 
dissolved silica, a consequence of the high amorphous silica 
content of grains, particularly the malt husk (ler, 1955). In an 
old copy of Moore’s Universal Assistant and Compleat 
Mechanic, Longyear (1941) found the following recipe for pet- 
rifying wood: *‘Gum salt, rock alum, white vinegar, and peb- 
bles powder, of each an equal quantity. Mix well together. If, 
after the ebullition is over, you throw into this liquid any wood 
or porous substance, it will petrify it.”’ If this recipe, or Valen- 
tine’s, or Kentmann’s, does truly lead to petrifaction, it has yet 
to be demonstrated. Experimental verification of the alleged 
results is prevented, however, either because of insufficiency 
of procedural information given or because of uncertainty re- 
garding the true chemical nature of the actual materials used. 
In more recent times, Schulze and Theden found that an 
aqueous solution of sodium metasilicate can be easily trans- 
ported through the ray cells and into the tracheids of fresh pine 
wood (Buurman, 1972). Later, Drum (1968a, 1968b) was able to 
show that cellular detail in vascular tissue can indeed be rep- 
licated in silica by artificial means. By first soaking fresh birch 
twigs in sodium silicate solution for 12 to 24 hours and then 
wet-ashing the impregnated twigs in chromic acid for two to 
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