554. The alder-tree is a native of Europe and Asia, growing in wet grounds and by the banks of rivers. The tree seldom exceeds 40 feet in height, and 24 inches diameter, except in very favourable soils, when it has been known to attain a height of 60 feet, with a diameter of 30 inches.

The wood is extremely durable in water or wet ground Vitruvius has remarked, that in a wet state it will sustain the weight of very heavy piles of building without risk of accident; and that the whole of the buildings at Ravenna, which is situate in a marsh, were founded upon piles of this wood.* Evelyn says, he finds they used it under that famous bridge at Venice, the Rialto, which was built in 1591, or 280 years ago. But it soon rots when exposed to the weather, or to damp; and in a dry state it is much subject to worms.

On account of the durability of alder in water, it is es-teenmed valuable for piles, planking, sluices, pumps, and in general for any purpose where it is constantly wet. And for such purposes it has been much cultivated in Holland and Flanders. It is also used for turners' wares and other light purposes. Our ancestors used it for scaffolding.†

The colour of alder is reddish yellow, of different shades, and nearly uniform. The texture is very uniform, with the larger rays of the same colour as the wood, therefore not very distinct, nor producing a flowered appearance when wrought.

It is soft, and works very easily; would cut well in carving, and make very good models for casting from.

The cohesive force of a square inch of alder varies from 5000 to 13.900 lbs.; its modulus of elasticity is 1,086,750 lbs. for a square inch; and a cubic foot weighs from 34 to 50 lbs. in a dry state.

* 'Vitruvius,' book ii., chap, ix , and book iii., chap. iii. † Britton's ' Architectural Antiquities,' vol. iii., p. 31.