OF SUTHERLAND AND CAITHNESS. 
47 
tioned, are not particularly suitable for the nesting of rock birds. 
Few fissures and still fewer ledges are formed, and only where 
faults occur in the general incline can a few guillemots find lodge- 
ment. Even the under-cliff at places shows an inclination of about 
22° to the north-west. 
Following the Holborn coast-line eastwards a very fine stack 
of rock called " The Clett " is seen embayed by a narrow gdc 
and by Holborn Head. It is perhaps half an acre in extent of 
top-surface, and is populated by a great colony of herring-gulls, 
the young of which on the 28th of June were nearly half as large 
as their parents. A large colony also of guillemots were resting, 
huddled together, on the seaward rise of the Clett, and on the 
south-east side of the same stack they found nesting-gi'ound, 
because here the dip of the strata being inwards towards the rock, 
not outwards towards the sea, their eggs cannot roll off. 
IsTear the Headland are several fine examples of " swallows " or 
" creux," or, locally, " blow-holes," great holes piercing down- 
wards to the "gloops"^ beneath: the hollow boom of the sea waves 
coming up in regular cadence to tlie ear, though the waves them- 
selves were often invisible. 
Most remarkable amongst these is " The Devil's Bridge." This, 
originally no doubt a " blow-hole," has after much travail by the 
forces of Nature been opened out seaward. It faces the outer side 
of the Clett, but at the top is bridged over by an apparently im- 
moveable and mighty mass of pavement, some 15 feet in perpendi- 
cular thickness. Lower down the chasm, into which one can descend 
with ease for some distance, it is again spanned by a mass of rock. 
A photograph alone can give an adequate idea of the grandeur 
of this half-creux, half-goe, and of the Clett seen through the 
opening. 
We visited the lighthouse at Holborn Head on one occasion, 
and found it as it had been described, not a favourable position for 
the observation of migratory birds. Not a bird had appeared at the 
light since May 1884 up till the date of my visit in June 1885. 
In the neighbourhood of Dunnet are extensive sandhills, called 
Sea-caves where tlie tide strikes and throws out the air witli force. 
