334 
produced by the filling up of little cracks in the stone, by a sub- 
sequent infiltration of a silicious fluid. Its fracture is conchoidal, 
very rarely splintery ; its lustre is dull, and its hardness varies with 
its proportion of silex. The general characters and properties are 
such, as readily lead to a knowledge of the nature of its composition. 
The veined or cloudy appearance of these stones may, in general, be 
very easily traced to the introduction of fine earthy particles, between 
the detached masses of bituminized fibres of the fossil wood, which 
have been all consolidated together by a subsequent infiltration of a 
solution of silex. The specimen, of which the polished section is 
figured at Plate II. Fig. 8. will serve to point out how much this 
opinion is favoured by the appearances yielded by this species of 
wood. The examination of jaspers has shown that they generally 
contain silex and alumine, and even other earths, in different pro- 
portions j whilst the following experiments corroborate the idea of 
bituminous matter entering, in a small proportion, into the composi- 
tion of this species of fossil wood. 
Sixty grains of jasperized wood, reduced to powder, were mixed 
with double the quantity of purified pot-ash, purified by Mr. Allen, 
to which was added a sufficient quantity of distilled water, to dis- 
solve the pot-ash. The powder which settled, and which was nearly 
white when dry, but became darker on being wetted, in about four 
or five days, showed a line ot darker matter on the surface of the 
precipitate ; which, during a month, continued to increase, when it 
seemed to constitute, in hulk, about one fourth of the whole preci- 
pitate. Half this precipitate, added to colourless sulphuric acid 
evidently darkened it : but willing to avail myself of the kindness of 
my friend Mr. W. H. Pepys, whose well-known abilities would stamp 
unquestionable authority on the results of his experiments, I re- 
quested that gentleman to subject the remainder to an examination, 
for the purpose of ascertaining the presence of carbon. According 
to his obliging communication— the separated precipitate, after 
