The Spiders Exodus 163 



have a bridge whereby to cross the intervening 

 space. This bridge, which I cannot see, I can 

 at least destroy. I cleave the air with a ruler 

 in front of the Spider making for the window. 

 That is quite enough : the tiny animal at once 

 ceases to go forward and falls. The invisible 

 foot-plank is broken. My son, young Paul, 

 who is helping me, is astounded at this wave 

 of the magic wand, for not even he, with his 

 fresh, young eyes, is able to see a support ahead 

 for the Spiderling to move along. 



In the rear, on the other hand, a thread is 

 visible. The difference is easily explained. 

 Every Spider, as she goes, at the same time 

 spins a safety-cord which will guard the rope- 

 walker against the risk of an always possible 

 fall. In the rear, therefore, the thread is of 

 double thickness and can be seen, whereas, in 

 front, it is still single and hardly perceptible 

 to the eye. 



Obviously, this invisible foot-bridge is not 

 flung out by the animal : it is carried and 

 unrolled by a gust of air. The Epeira, suppHed 

 with this line, lets it float freely ; and the wind, 

 however softly blowing, bears it along and 



