102 THE STORY-BOOK OF SCIKNTK 



silken structure is at first transparent enough to per- 

 mit one to see the caterpillar at work ; but as it grows 

 thicker what passes within is soon hidden from view. 

 What follows can easily be guessed. For three or 

 four days the caterpillar continues to thicken the 

 walls of the cocoon until it has exhausted its store 

 of liquid silk. Here it is at last, retired from the 

 world, isolated, tranquil, ready for the transfigura- 

 tion so soon to take place. Its whole life, its long 

 life of a month, it has worked in anticipation of the 

 metamorphosis ; it has crammed itself with mulberry 

 leaves, has extenuated itself to make the silk for its 

 cocoon, but thus it is going to become a butterfly. 

 What a solemn moment for the caterpillar ! 



"Ah! my children, I had almost forgotten man's 

 part in all this. Hardly is the work of the cocoon 

 finished when he runs to the heather sprig, lays vio- 

 lent hands on the cocoons and sells them to the man- 

 ufacturer. The latter, without delay, puts them into 

 an oven and subjects them to the action of burning 

 vapor to kill the future butterfly, whose tender flesh 

 is beginning to form. If he delayed, the butterfly 

 would pierce the cocoon, which, no longer capable of 

 being unwound on account of its broken threads, 

 would lose its value. This precaution taken, the 

 rest is done at leisure. The cocoons are unwound 

 in factories called spinning mills. They are put 

 into a pan of boiling water to dissolve the gum which 

 holds the successive windings together. A work- 

 woman armed with a little heather broom stirs them 

 in the water, in order to find and seize the end of 

 the thread, which she puts on a revolving reel. Un- 



