66 THE OLD RED SANDSTONE. 
be wished than hoped for —a circumstance within the bounds 
of the possible, but beyond those of the probable. Could 
the working-man of the north of Scotland have so much as 
dreamed that he was yet to enjoy an opportunity of compar- 
ing his observations with those of the naturalist of Neufchatel, 
and of having his inferences tested and confirmed ? 
The opportunity did occur. ‘The working-man did meet 
with Agassiz; and many a query had he to put to him; and 
never, surely, was inquirer more courteously entreated, or his 
doubts more satisfactorily resolved. ‘The reply to almost my 
first question solved the enigma of nearly ten years’ standing. 
And finely characteristic was that reply of the frankness and 
candor of a great mind, that can afford to make it no secret, 
that, in its onward advances on knowledge, it may know 
to-day what it did not know yesterday, and that it is content 
to ‘“‘ gain by degrees upon the darkness.” ‘* Had you asked 
me the question a fortnight ago,” said Agassiz, ‘* 1 could not 
have replied to it. Since then, however, | have examined 
an ichthyolite of the Old Red Sandstone in which the verte- 
bral joints are fortunately impressed on the stone, though 
the joints themselves have disappeared, and which, exactly 
resembling the vertebree of the shark, must have been carti- 
laginous.” Ina subsequent conversation, the writer was grati- 
fied by finding most of his other facts and inferences authen- 
ticated and confirmed by those of the naturalist. I shall 
attempt introducing to the reader the peculiarities, general 
and specific, of the ichthyolites to which these facts and ob- 
servations mainly referred, by describing such of the families 
as are most abundant in the formation, and the points in 
which they either resemble or differ from the existing fish of 
our seas. 
Of these ancient families, the Osteolepis, or bony-scale, 
