194 Prof. C. Lapworth—The Secret of the Highlands. 
in his eyes is this visible physical evidence. When, however, his 
survey is completed, he frequently discovers that his successive 
“‘formations,”’ distinct as they appear lithologically, present a wonder- 
ful identity in organic remains through thousands of feet of vertical 
extent, when the fossils are regarded en masse; but show the most 
vital difference in their minor horizons, only a few yards apart, when 
the species are considered in detail. Such astounding paleonto- 
logical phenomena he would scorn to acknowledge as probable or 
even possible in the Neozoic rocks. But the physical evidences at 
his command in these ancient convoluted strata appear unquestion- 
able. There can, therefore, he imagines, be but one possible solution 
of the enigma. These paleontological difficulties are probably due 
in some mysterious way to the effects of migration, and may be 
safely ignored altogether. The outsider is left to draw for himself 
the implied conclusion: the dogma of “strata identified by super- 
position and organic remains” is of paramount consequence in the 
gently inclined, unbroken and varied recent formations; but in 
crumpled, dislocated and monotonous Lower Paleozoic strata such 
fossils as are discoverable are of no special stratigraphical value ; 
the apparent superposition of the several recognizable rock-groups 
is the sole and sufficient clue to the original order of the beds. 
This highly unsatisfactory method of eluding the difficulty I have 
long resisted to the best of my ability. In all those cases which 
I have myself been able to investigate, the asserted discrepancies 
between the physical and paleontological sequences have entirely 
disappeared wherever the strata admit of being worked out zone by 
zone. The difficulties of this task, however, are so great, and the 
natural tendency to rely upon apparent superposition so irresistible, 
that I feel assured that in some of its minor points my earlier 
work needs revision in the light of more recent discoveries. But 
the detailed paleontological sequence developed by the method 
of zones by myself several years ago among the convoluted Moftat 
rocks of South Scotland has been subsequently confirmed, as I shall 
show elsewhere, to an extent, and with a minuteness, which, even 
in my most sanguine moments, I hardly dared to anticipate. 
In labouring to discover the original order of succession in such 
of the Lower Paleozoic rocks as are excessively convoluted, I find 
that the ordinary broad rules of British stratigraphy, as laid down 
in our text-books, are inadequate to the task. But they are not 
superseded, they are merely supplemented by a few additional prin- 
ciples applicable more especially to mountain regions. Even these 
additional principles are not new. Buried in the note-book of the 
mountain geologist, or in little studied foreign scientific publications, 
they have not yet made their way into our authoritative text-books. 
I intended to publish some of my own conclusions upon the subject 
in the second part of my paper upon the “ Girvan Succession,” and to 
demonstrate their utility by showing how their application reduces 
to naturalness and symmetry the awkward-looking preliminary 
sketch-map of the region, as there developed almost wholly by the 
presently accepted rules of British stratigraphy. But the light 
