APPENDIX. 
151 
were found many fragments of bone and mineralized wood, 
in some instances lying entirely loose upon the sand, in 
other cases half buried in it, with their upper portions 
projecting, naked, and exposed to the air: they appeared 
to have been left in this condition, in consequence of the 
matrix of sand and gravel that once covered them under¬ 
going daily removal by the agency of winds and rains, and 
they would speedily have fallen to pieces under this ex¬ 
posure to atmospheric action, had they not been protected 
by the mineralization they have undergone. 
On examining many of the ravines that intersect this 
part of the country, and which were at this time dry, the 
same silicifled wood was found projecting from the sand¬ 
banks, and ready to drop into the streams; from the bot¬ 
toms of which the travellers took many fragments, that 
had so fallen during the gradual wearing of the bank, and 
lay rolled and exposed to friction by the passing waters. 
Some of these stems were from fifteen to twenty feet in 
length, and five feet in circumference. These circum¬ 
stances show, that the ordinary effect of existing rains and 
torrents is not only to expose and lay bare these organic 
remains, but wash them out from the matrix to which 
some other and more powerful agency must have intro¬ 
duced them. 
Of the total number of bones in this collection, about 
one-third have suffered from friction; and of the remain¬ 
der, nearly all appear to have been broken, more or less, 
before they were lodged in the places where Mr. Crawfurd 
found them irregularly dispersed. Many fragments also 
of the ivory have been rolled considerably; but no one 
specimen of that substance, or indeed of any bone in this 
collection, has been reduced to the state of a perfect peb¬ 
ble : from this circumstance we may infer, that the waters 
