The Processionary : the Procession 



interesting. I have thought out another, one 

 more fertile in possibilities. I propose to 

 make the caterpillars describe a close circuit, 

 after the ribbons running from it and liable 

 to bring about a change of direction have been 

 destroyed. The locomotive engine pursues its 

 invariable course so long as it is not shunted 

 on to a branch-line. If the Processionaries 

 find the silken rail always clear in front of 

 them, with no switches anywhere, will they 

 continue on the same track, will they persist 

 in following a road that never comes to an 

 end? What we have to do is to produce this 

 circuit, which is unknown under ordinary con- 

 ditions, by artificial means. 



The first idea that suggests itself is to seize 

 with the forceps the silk ribbon at the back 

 of the train, to bend it without shaking it and 

 to bring the end of it ahead of the file. If 

 the caterpillar marching in the van steps upon 

 it, the thing is done : the others will follow 

 him faithfully. The operation is very simple 

 in theory but very difficult in practice and 

 produces no useful results. The ribbon, which 

 is extremely slight, breaks under the weight of 

 the grains of sand that stick to it and are 

 lifted with it. If it does not break, the cater- 

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