322 NATURE'S TEACHINGS. 



much like that of trying to break a piece of coal by pinching 

 it with the tongs. 



The left-hand figure of the illustration represents part of the 

 jaws of the Wolf-fish, or Sea- wolf, as it is sometimes called, 

 and a very wonderful crushing machine it is. The Sea-wolf 

 (Anarrhicas lupus), sometimes called the Sea-cat, or Swine- 

 fish, is tolerably common on our coasts, and, as it sometimes 

 attains a length of seven feet, and is proportionately stout and 

 muscular, the power of its bite may be estimated. The fish in 

 question feeds chiefly on Crustacea and hard- shelled molluscs, 

 and is therefore furnished with an apparatus which can crush 

 their shells. Extremes meet. The Sea- anemones, which are 

 mere films of animal matter, and can be torn in pieces with 

 the finger and thumb, can seize, swallow, and digest a crab or 

 an oyster in spite of the thick and strong shells in which they 

 are enclosed. So can the Sea-wolf, and fishes of a similar 

 character. But nothing intermediate can touch them, and it 

 is curious to reflect that such opposite means should produce a 

 similar effect. 



On reference to the illustration, the reader will see how 

 exact is the parallel between the Nut-crackers and the Sea- 

 wolf's jaws, both being worked on the same principle, and 

 both being furnished with a series of projecting points, which 

 are used for the purpose of preventing the escape of the object 

 which is to be crushed. The terrible grasping power of the 

 crocodile, the dolphin, and other predacious creatures can be 

 explained on the same principle. 



THE ROLLING-MILL. 



WE now come to another variation of the Crushing Machine, 

 i.e. that in which the motion is constant, and not intermittent, 

 as is the case with those machines which have just been 

 mentioned. 



Perhaps some of my readers may have visited those great 

 iron- works in which huge masses of iron are rolled into plates 

 of greater or less thickness, or are cut up into strips as easily 

 as if they were butter. 



The mechanism is in its principle simple enough. The 

 cylindrical rollers are placed nearly in contact, and forced 



