Not only do these wooden islands evince much mechanical and technical skill on the part of their founders, but, what is still more singular, their area of distribution appears to have been co-extensive with the districts formerly occupied by Celtic races. Hence we have here another proof of the extraordinary vigour, intense individuality, and plastic character of early Celtic civilisation, in thus developing, from its own inherent resources, a unique form of stronghold, simple in structure, but yet admirably adapted to the unsettled conditions of life and military requirements of the period. SECTION IV. _Topographical Changes in the Lake-Dwelling Area during or subsequent to the Period of their Development._ _Supposed Change in Climate, and its effects._--The arguments in support of the theory that a material deterioration has taken place in the climate of Britain since the Roman period are generally based on the following considerations:-- (1.) _Historical Statements._ Roman historians agree in representing the climate as humid, but so mild that the natives went about in a semi-nude condition, favourable to luxuriant vegetation, and not so cold as that of Gaul. Thus Cæsar expressly states that all kinds of trees grew in Britain, except the _fir_ and the _beech_, and that the climate was more temperate than in Gaul. Tacitus describes the climate as always damp with rains, and overcast with clouds, without, however, intense cold being even felt. In the speech attributed to Galgacus, previous to the battle of Mons Grampius, he says that their "bodies and limbs were worn out by cutting down woods, draining bogs, stripes, and outrages;" and the same historian, in describing the result of a previous engagement in Fifeshire, in which the Caledonians were beaten, states that "had not the woods and marshes favoured their retreat, this victory in all probability would have put an end to the war." Another writer (Dion Cassius) describes the Caledonians as dwelling in tents, naked, and without shoes; enduring hunger, cold, and all manner of hardships with wonderful patience; and capable of remaining in bogs for many days immersed up to the neck, and without food. In the woods they lived on the bark of trees and roots, and had a certain sort of food always ready, of which, if they took but the quantity of a bean, they would neither be hungry nor dry for a long time after. Herodian also describes them as going about partially naked to prevent the beautiful figures painted on their bodies from being hidden. According to him, they used iron as other barbarians did gold, both as an ornament and sign of wealth. They wore neither coat of mail nor helmet to prevent being encumbered in their marches through bogs and mosses, whence such a quantity of vapours was exhaled that the air was always thick and cloudy. (2.) _The numerous remains of forest trees found in bogs and mosses in localities where, at the present time, no such trees are found to grow._