pose of directing the
navigation of the Clyde. At that early date, which I think we may throw
far back in the space of the six centuries of the estimate, or may even
throw further back still, the Clyde was mainly navigated by canoes of two
feet or so in depth, though we ought to have statistics of remains of
larger vessels discovered in the river bed. {49a} I think we may say
that the finances of Glasgow, in St. Kentigern's day, about 570-600 A.D.,
would not be applied to the construction of Dr. Munro's "tower with its
central pole and very thick walls" {49b} erected merely for the purpose
of warning canoes off shoals in the Clyde.

That the purpose of the erection was to direct the navigation of Clyde by
canoes, or by the long vessels of the Viking raiders, appears to me
improbable. I offer, _periculo meo_, a different conjecture, of which I
shall show reason to believe that Dr. Munro may not disapprove.

The number of the dwellers in the structure, and the duration of their
occupancy, does not affect my argument. If two natives, in a very few
years, could deposit the "veritable kitchen midden," with all the sawn
horns, bone implements, and other undisputed relics, we must suppose that
the term of occupancy was very brief, or not continuous, and that the
stone structure "with very thick walls like the brochs" represented
labours which were utilised for a few years, or seldom. My doubt is as
to whether the structure was intended for the benefit of navigators of
the Clyde--in shallow canoes!

IX--A GUESS AT THE POSSIBLE PURPOSE OF LANGBANK AND DUMBUCK

The Dumbuck structure, when occupied, adjoined and commanded a _ford_
across the undeepened Clyde of uncommercial times. So Sir Arthur
Mitchell informs us. {51a} The Langbank structure, as I understand, is
opposite to that of Dumbuck on the southern side of the river. If two
strongly built structures large enough for occupation exist on opposite
sides of a ford, their purpose is evident: they guard the ford, like the
two stone camps on each side of the narrows of the Avon at Clifton.

Dr. Munro, on the other hand, says, "the smallness of the habitable area
on both "sites" puts them out of the category of military forts." {51b}
My suggestion is that the structure was so far "military" as is implied
in its being occupied, with Langbank on the opposite bank of Clyde by
keepers of the ford. In 1901 Dr. Munro wrote, "even the keepers of the
watch-tower at t