690 Peculiarities in the Nets 



a small bit of gravel, at its lower extremity ; and thus forming 

 a pendulum which, by its weight, kept the net in the requisite 

 degree of tension, and, in fact, more conveniently than if it 

 had been fixed, as allowing the net to vibrate more gently to 

 the impulse of any sudden gust of wind ; and at the same time 

 the pendulums, giving way to the slightest touch, were not 

 injured by coming into contact with any accidental pedes- 

 trian, as 1 frequently observed. That the due tension of the 

 nets depended on these pendulums, I ascertained by repeated 

 trials ; for, on gently detaching the twig, or leaf, or gravel, at 

 the end of the line, the net immediately collapsed, and blew 

 about in all directions, evidently unfitted for its purpose of a 

 snare. [See p. 74? 7.] 



These pendulums, when I first observed them, puzzled me 

 a good deal. If the weights had been always simply dead 

 leaves or twigs, I should at once have considered them as 

 accidental, and arising from the spider having attached its 

 third point of support to a dead leaf or twig (on the neigh- 

 bouring tree) ; which, afterwards giving way from the force of 

 the wind, hung down ; and, from its weight and the length of 

 the attached line forming a sufficient counterpoise to keep the 

 net duly stretched, the spider was either not aware of the 

 change, or was satisfied with the performance of her net in its 

 new position. 



It was not, however, so easy to account for the pendulums 

 ballasted by bits of gravel, varying in size from that of a 

 small pea to that of a horsebean, as the first eight or ten of 

 those which I noticed were attached to nets stretched between 

 the stems of lofty trees at the height of 10 ft. or 12 ft. from 

 the ground, the line of the pendulum being 6 ft. to 8 ft. long, 

 and the gravel vibrating backwards and forwards at the height 

 of 3 ft. or 4 ft. from the ground ; but, on careful examination 

 of many nets, I at length met with one which seemed to 

 throw light on the difficulty. In this the gravel of the pen- 

 dulum rested partly on the ground ; and hence it might be 

 inferred that the spider, wanting a point of support for the 

 lower end of the triangle enclosing its net, had let itself 

 drop to the ground, and there fixed its line to one of the 

 pieces of gravel, possibly without being aware of its being 

 a movable object ; and of which the elevation from the sur- 

 face seen in other instances, might be owing to the spider 

 having pulled up the main line of her net in the process of 

 strengthening it by new lines running from it to some more 

 elevated part of the tree, which operation would proportion- 

 ally lift up the pendulum. 



These gravel pendulums, therefore, are most probably, as 



