496 Improvement i?i Naval Architecture, &fc. 



also be used with those masts, and will not cost half the ex- 

 pense of rope, while they will also prove ten times more du- 

 rable. For many other purposes in shipping, wrought iron, 

 employed as a substitute for the materials now in use, would 

 liave as great advantages as in the articles above mentioned. 

 Even the whole hull may be made of wrought iron. 



IV. Preparation of Ship Timbers, and improved System 



()f Building. 



*' For a long period the only means employed to effect 

 the bending of ships' planks was by exposing them to the 

 heat of open fires, and in most parts of Europe this is still 

 the practice. As hitherto conducted, it has been found to 

 be a tedious slovenly process, attended with a great expense 

 of fuel, and unequal in its effects, some parts being only 

 partially heated, while others are burnt. 



" Another system was therefore resorted to, thatof eni- 

 ploying steam ; and it must be allowed that this mode of 

 bending has been found to answer so far as the interest of 

 the ship-builder is concerned; but the ship-owners have 

 suffered from its effects. It is possible by means of steam 

 to give the required degreeof flexibility to planks; but steam 

 of a degree ot temperature high enough lo destroy the ve- 

 getable sap cannot be confined in vessels of any reasonable 

 strength. Wood so treated has been found liable to sudden 

 decay : nor is this, which is an important objection, the 

 only one to which steaming is liable. When planks be- 

 yond a certain thickness are bent in this way, they are 

 found to be injured from the temperature being too low to 

 give the required flexibility ; and, owing to the want of a 

 better method, the curving of strong limbers has hitherto 

 been impiacticablc. 



*' It is well known that the decay of a ship originates 

 and takes place in the tin^bers and inside the planks, by 

 their being precluded from a free circulation of air to eva- 

 porate the natural vegetable sap of the wood. 



" The process now recommended is for heating both 

 planks and timbers, without steam, and in such a manner 

 that they n'ay be enveloped and equally surrounded on all 

 sides with hot air and smoke ; the coal tar contained in the 

 latter entering at the same time the pores of the wood, and 

 acting as a feeder. This process is so conducted as to pre- 

 vent the wood from being burnt by it : all the air that 

 reaches the timbers, while under process, being previously 

 obliged to pass through the fire, and being, by that means, 



dej5rived 



