308 Obfervations on the Flints of Chalk-beds. 
light I confider the white opake fpots, fo commonly 
appearing in the fubftance of flints. 
Mr. Dolomieu ( Fournal de Phyfique, 1792) has 
related, experiments, from which he concludes, that 
filiceous matter in.a ftrong heat yields hydrogene 
air. His experiments are not indeed perfectly deci-. 
five; becaufe the air might have come from the: 
alkali, with which he fufed his filiceous earth. 
Should it however come from the flint, the fa& 
would furnifh an explanation of the appearances I 
have defcribed. ; Streaks or weals may fometimes be 
obferved upon. the internal furface of hollow flints. 
I have feen thefe flreaks round, and dilated at their 
termination. ‘They muft, I imagine, have been 
formed by vifcid matter running upon the infide of 
the nodule, Exactly the fame appearance might be 
produced, by letting flow down the infide of a tea- 
cup a liquid, too tenacious to run off the fide 
entirely, but thin enough to reach the bottom, and 
form a fmall button there. If we could fuppofe, 
with Dr, Hutton, that flints were fpouted into the 
body of the chalk from fubterraneous fires, we 
might imagine the furface of each clot to have been 
cooled by coming into contact with the chalk, or 
during its paflage, while the internal parts continued 
to boil and bubble, and work themfelves into foam 
or powder. I cannot however conceive, how the 
nodules and tables could have been arranged, in the 
manner they are, by injection. 
V. Balls 
