AN ERROR OF JUDGMENT 



the first, leaving between the two a little wall about a 

 quarter of an inch in height. 



When ants trace out the plan of a wall, chamber, or 

 gallery in this independent manner, it sometimes happens 

 that the various parts of the work do not fit in with one 

 another. This is by no means an infrequent occurrence, 

 but the ants are not embarrassed by it, and I will now tell 

 you of an instance in which the workman found out his 

 mistake and knew how to rectify it. 



A wall had been raised with the apparent object of sup- 

 porting a vaulted ceiling, still unfinished, which stretched 

 from the opposite side of a large chamber. The workman 

 who had begun this had made it not quite high enough to 

 meet the wall on which it was to rest, and if it had been 

 continued on the original plan it must have met the wall 

 about half-way up a thing to be avoided. I was very 

 much interested in this circumstance, when one of the ants 

 arrived and after visiting the works appeared to be struck 

 with the same difficulty, for it at once began taking down 

 the ceiling and raising the wall on which it had rested. 

 Then, as I looked on, it constructed a new ceiling out of the 

 fragments of the old one. 



When the ants begin an undertaking, one would suppose 

 that they were working on a plan thought out beforehand 

 and then carried out. Thus when an ant discovers two 

 stems of grass upon the nest, lying crossways, in a position 

 which favours the construction of a lodge, or some little 

 beams which suggest its sides and corners, it examines the 

 various parts and then sets out in a very workmanlike 

 fashion to fill in the spaces along the stems with tiny parcels 

 of earth, taking suitable materials from all quarters, and 

 sometimes not hesitating to destroy for this purpose the 

 work begun by others, to such an extent is it dominated by 



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