As regards the durability of the two species of oak, Mr.

* Ray's 'Synopsis, etc.,' p. 440. ' Flora Brit.,' vol. iii., 1026-7.

† These trees were first pointed out to the author by his brother Mr. R. Tredgold, whose assistance in collecting and examining specimens of the leaves, fruit, and wood of these and other trees was very useful.

Fincham relates an experiment made in the year 1832. "The late Navy Board having, in the year 1830, directed a quantity thereof to be supplied to Portsmouth Dockyard, and to be tried 'as thick stuff or plank in the sides of a ship, or as timber in her gun-deck beams.'

"At that time the timber of the Q. sesslliflora was supposed to be so deficient of durability that the order of the Navy Board to use these descriptions of oak, 'one kind against the other,' included a special caution 'not to place it in situations where it would be difficult and expensive to remove it, in consequence of the number of fastenings that would go through it.' The timber was, therefore, suitably applied in building the ' Vindictive,' forty pieces of the Q. robur (pedunculata) were placed on the starboard side, and forty pieces of the Q. sessiliflora on the port side.

"At the expiration of seventeen years the course of the experiment was examined. It was then found that in the short stuff placed between the ports the two kinds of oak were equally sound; but in the planking upon the outside of the ship the Q. sessiliflora was found in a better state of preservation than the Q. robur (pedunculata).

" So far as the evidence of the above experiment goes there appears to be no reason to prefer the Q. robur to the other species of oak for naval uses." *

Mr. Brown, in his ' Treatise on Forestry,' states, " At one time I considered the timber of the Q. sessiliflora inferior to that of Q. pedunculata; but from more extended observations on the subject of oak timber within the last ten years, I am now led to state that the timber of the one sort is for all purposes as good as that of the other. In some experiments which I made recently in regard to the comparative strength of the timber of the two kinds, I found that a beam of the sessiliflora bore fully a greater strain under a given weight than one of equal dimensions of the pedunculata. Indeed, for all purposes to which oak timber is applied, that of the sessiliflora is used as plentifully as that of the pedunculata, and in old buildings its durability has been found to be equal to the timber of the other kind." When young the timber of the sessiliflora is of a more open texture than that of the pedunculata of the same age; but as it becomes older it is found as compact and solid as the latter. This arises from the tree being of a more free growth in its young stages than the other is. It appears, as far as can be determined from the structure of the wood, that the fine oak found in old Gothic roofs is of the sessile-fruited kind. At the same time it must be owned that our means of judging are not so satisfactory as to enable us to decide on this point with certainty; but we know that the old oak is very durable.

* ' Outline of Ship-building,' 3rd edit., p. 13.

The strength, elasticity, toughness, and hardness of the sessile-fruited oak render it superior for ship-building; it is, however, both heavier and more difficult to work than the common oak. The wood for the old ' Sovereign of the Seas' was from the north,* and it is probable that the greater part of it was of the sessile-fruited oak. The hardness of the timber "when taken in pieces after forty-seven years' service" is in favour of this conjecture.

In order to make experiments on the two species, when grown at the same place, and nearly of the same age, the author was supplied by Mr. Atkinson with specimens from trees grown at the Deepdene, near Dorking, Surrey, which were directed by the proprietor, Mr. Hope, to be cut for the express purpose of comparing the woods.

The trees were cut a little before the fall of the leaf, and being sawed into small scantlings, after drying two months they were submitted to experiment.

The following Table shows the results of trials on two of the pieces, each being an inch square, sustained by supports 24 inches apart, and the weight applied in the middle of the length.

* ' Encyclopaedia Britannica,' art. Dry Rot.

Both these specimens broke short without splitting, therefore these experiments offer a very fair view of the properties of the two species. The sessiliflora bent considerably more at the time of fracture than the pedunculata, but it could not be measured with that correctness which is necessary to render such data useful.

The following Table contains the values of the cohesive force, and modulus of elasticity, calculated from the above experiments.

These pieces were hastily and therefore imperfectly seasoned; but as they were treated exactly alike this would not affect the comparison.

Similar results in favour of the sessiliflora were obtained in experiments made on six pieces which had been cut out of the specimens used in the 'Vindictive,' as follows: -

Each piece was 2 inches square and 6 feet long between the supports; the load being placed on the middle.

541. There is another kind of oak called the Durmast Oak, said to be a variety of the Q. sessiliflora, which is a native of France and the south of England. The wood is not so strong nor of so firm a texture as the English oak, and the tree retains its foliage to a much later period in the season.

542. A considerable quantity of oak is exported from Norway, also from Riga, Dantzic, Memel, and other ports in the Baltic Sea: to what species it belongs has not been clearly ascertained. It is distinguished from the British oak, to which it is inferior, by the straightness of its grain and freedom from knots. Dantzic oak is much used in planks for the bottoms of ships, for decks and other purposes. The wood is close-grained and compact, though sometimes the grain is rather short. Memel oak is finer in grain than the Dantzic oak. It is clean and well adapted for the best descriptions of millwrights' and shipwrights' work. Oak is also exported from Norway, under the name of "Clapboard," and from Holland under the name of "Dutch Wainscot." The latter is grown in Germany, from whence it is floated down the Rhine for exportation. Wainscot may be easily distinguished from clapboard, to which it is superior, by the absence of the white-coloured streaks, which cross the former in all directions. These are less liable to warp and split when in thin boards than English oak, but are much softer, and in other respects inferior to it.