24 NATURE'S TEACHINGS. 



Next we come to the boat-hook, which is so useful either as 

 a temporary anchor, or as a pole by which a boat can be pro- 

 pelled by pushing it against the shore or the bed of the water ; 

 and then to the " punt-pole," which is only used for the latter 

 purpose. 



Lastly, we come to the life-belt and life-raft, which are now 

 occupying, and rightly, so much of tho public attention. These 

 subjects will be treated in their order in the present chapter, 

 and I hope to be able to show the reader that in all these 

 points nature has anticipated art. 



I presume that most, if not all, of my readers are aware of 

 the rapidly extending use of iron in ship-building, not only in 

 the standing rigging, but in the material of the vessel. First 

 there came iron " knees/' i.e. the angular pieces of wood 

 which strengthen the junctions of the timbers. . Formerly 

 these were made of oak-branches, and, as it was not easy 

 to find a bough which was naturally bent at such an angle as 

 was required for a "knee," such branches were exceedingly 

 valuable. Iron, however, was then employed, and with the best 

 results. It was lighter than the wooden knee, was stronger, 

 could be bent at any angle, and took up much less space. 



By degrees iron was used more and more, until vessels were 

 wholly made of that material. Then the masts, and even the 

 yards, were made of iron, and, strange as it may appear, were 

 found to be lighter as well as stronger than those made of 

 wood. Of course, the masts and yards were hollow, and it was 

 found by the engineers that in order to combine lightness with 

 great strength, the best plan was to run longitudinal ridges 

 along the inside of the tube. 



A section of one of these masts is given at Fig. B, and 

 taken from the drawings of one of our largest engineering 

 firms. The reader will see that the mast is composed of rather 

 slight material, and that it is strengthened by four deep though 

 thin ribs, which run throughout its length. 



When I first saw this mast I was at once struck with the 

 remarkable resemblance between it and the quill of the Porcu- 

 pine. These quills, as all anglers know, are very light, and 

 of extraordinary strength when compared with their weight. 

 Indeed, they are so light that they are invaluable as penholders 

 to those who are obliged to make much use of their pen. I 



