33 
this new order. But as confusion might arise, from employing the 
same word to describe both the class and the order, it was recom- 
mended by Sir John Hill, for the sake of precision, to annex to the 
word fossil, when expressive of the order, the epithet extraneous or 
adventitious. 
As none of the terms, hitherto enumerated, at all marked the 
change which had taken place in the nature of the substance, this 
was proposed to be expressed by adopting the term petrifaction. 
The prevailing practice with writers in mineralogy appears at pre- 
sent to be, either the employment of the last mentioned term ; or 
the annexing one or the other of the adjectives (" adventitious or extra- 
neousj to the substantive (fossil,) whilst in the common language 
of those most conversant with these substances, the idea is conveyed 
by the substantive alone. 
The more antiquated, and less significant of these modes of 
expression, do not demand any farther notice. Those alone, which 
have been adopted since the discovery of the real nature and 
origin of these substances, demand that examination, which a 
conviction of the necessity of establishing certain and determined 
modes of expression, obliges me, with hesitation and diffidence, to 
undertake. 
Petrifaction^, a word very frequently adopted, is certainly 
quite unqualified to be admitted, as the general term for these sub- 
stances ; since it refers, only to a conversion into stone ; whilst the 
changes, which actually take place, are of various kinds : and, in 
some instances, as in pyTitous fossils, the conversion is into a sub- 
stance, almost as widely different from stone, as from the matter of 
which the body originally consisted. It, therefore, can be employed 
to describe only that one particular species of fossils. 
Petrificata dicuntur vegetabilium vel aniraantium corpora, in substantiam fossilium 
niutEtEi Gesner, 
VOL. I. P, 
