34 Mr. W. Pengelly on the Red Sandstones, 
longitudinal or transverse vertical section they would appear as in 
fig. 4. Now, if each plate be permanently raised at one margin only, 
for example that nearest a. in each, a longitudinal vertical section 
through undisturbed as well as distui'bed plates would present the 
appearance shown in fig. 5 ; so that the re-arranged plates would 
project somewhat above the general surface. If, instead of the plates 
in a single linear series, those composing several contiguous and parallel 
lines in both a horizontal and a vertical direction, in other words all the 
plates within a limited and pretty constant breadth and depth and for 
a length of several inches, were thus permanently raised, and if, 
further, the transverse lines of plates in each horizontal section 
were curves, symmetrical with respect to each other and also with 
respect to the margins of the re-arranged area, as in fig. 6, the 
result would be very much such as the phenomenon I speak of. In 
fact the plates of sandy matter appear to have bristled up, here and 
there, in small sub -cylindrical masses. The coarser the material in 
which it occurs, the more obvious is the phenomenon, and this simply 
because the plates being larger and stronger, stand up in bolder 
relief. 
From the description just given it may probably be inferred that 
their axes invariably lie in the plane of sedimentation ; this 
however is by no means the fact, for they are sometimes found 
passing vertically, as well as at various degrees of obliquity, through 
the bed. Though commonly rectilineal they sometimes take a 
curvilineal direction ; nor are they always, even approximately, 
cylindrical, a transverse section being occasionally elliptical, and 
their outlines both curved and conical. Such instances, however, 
appear to be exceptional. 
They vary much in dimensions ; some examples being not more 
than a quarter of an inch in the transverse section, whilst others 
measure as much as three inches. In length they sometimes exceed 
a foot. 
In a few rare cases I have succeeded in drawing portions of them, 
three inches long, out of the rock in the form of cylinders ; as if 
they were casts of cylindrical tubes or galleries. 
Sometimes several appear to radiate from a centre, and not 
unfrequently they crOss one another and thus produce a rude 
reticulation on the surface of the rock. 
I can venture on no opinion as to their origin. They sometimes 
suggest the idea of the trails of marine invertebrata, but this could 
only apply, if at all, to those lying in the plane of sedimentation ; 
on other occasions I have been led to think them casts of the 
borings of animals in the sand. Should either of these guesses 
prove to be correct, they would give a special interest to the object 
as the only indications of organic existence yet found in the Red 
rocks of Devonshire. 
With the exception of certain, possibly, allied appearances in the 
