The transverse supports are the beams with their connecting systems of knees and carlings, the breast-hooks and transoms, and finally the decks themselves, which furnish both longitudinal and transverse support. Of late years it has been the custom to make the beams, knees, breast-hooks, and transoms of iron, and it is a very general idea amongst those who have not paid especial attention to the subject that this modification, taken in conjunction with the introduction of diagonal braces, constitutes composite construction, which is by no means the case. In the wooden construction the American and the English systems are very closely allied, whilst the French differs from both in many details. These differences are, however, in the detail work, a description of which would be scarcely warranted in the general summarizing of a system. The outside planking is made up of a series of strakes differing in thickness of plank in accordance with the points at which the greatest strains are brought by the motions of the vessel. Next the keel on each side, and tending to give it thorough support, are ranges of plank firmly secured in the rabbet of the keel and thicker than the planking in general, called the garboard strakes. Outside of the gun-deck beams is another range of heavy planking called the main wales, and in two and three decked vessels other strakes called middle wales are worked abreast the other beams. In the same way a great longitudinal strengthening is gained in the deck-planking by the outer range of planks next to the water-ways, called the thick strakes. It is considered that all these points are generally understood, and they are simply referred to on account of the necessity of bearing them in mind in following the developments. _Diagonal Construction._ This system of construction is found only in the English royal yachts and in their heavy wooden steam and sailing launches, but it is the opinion of an eminent English naval architect that had it not been for the very general introduction of iron in ship-building it would probably have taken precedence over the ordinary wooden construction. Its only objectionable feature is its expensiveness, while it is much superior in point of lightness and structural strength. Whilst in the ordinary wooden construction the weight of hull ranges between 46 and 54 per cent of the displacement, it is reduced in the diagonal system to between 32 and 40 per cent. [Illustration: Diagonal Construction.]