THE OLD RED SANDSTONE. 115 
at Cromarty, instead of those of Caithness and Gamrie, he 
might have employed the same terms, and remarked the same 
circumstances —the striated nodules, the mineral tar, the 
vegetable impressions, the absence of shells and zoophytes, 
the large-scaled, and double-finned ichthyolites— the pecu- 
liarities of which applied equally to the Dipterus and Diplop- 
‘erus —and the supposed tortoise, in which I once recognized 
the Coccosteus. It was much to know, that this doubtful 
formation — for as doubtful I still regarded it— was of such 
considerable extent, and occurred in localities so widely sepa- 
rated. I corresponded with the courteous author of the 
appendix, at that time General Secretary to the Northern In- 
stitution for the Promotion of Science and Literature, and 
Conservator of its Museum ; and, forwarding to him dupli- 
cates of some of my better specimens, had, as I had antici- 
pated, the generic identity of the Cromarty ichthyolites with 
those of Caithness and Gamrie fully confirmed. 
My narrative is, I am afraid, becoming tedious; but it em- 
bodies somewhat more than the mere history of a sort of 
Robinson Crusoe in Geology, cut off for years from all inter- 
course with his kind. It contains, also, the history of a forma- 
tion in its connection with science ; and the reader will, I 
trust, bear with me for a few pages more. Seasons passed ; 
and I received new light from the researches of Agassiz, 
which, if it did not show me my way more clearly, ren- 
dered it at least more interesting, by associating with it 
one of those wonderful truths, stranger that fictions, which 
rise ever and anon from the profounder depths of science, 
and whose use, in their connection with the human intel 
lect, seems to be to stimulate the faculties. I have often had 
occasion to refer to the one-sided condition of tail charac- 
teristic of the ichthyolites of the Old Red Sandstone. It 
