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XIII. — Observations on the Aranea geometrica, 
obtextrix, domestica, and other Spiders ; a?id 
particularly on the power they possess of fixing 
their threads horizontally, or at any degree of 
inclination, to two perpendicular bodies at a 
considerable distance from each other, so as to 
suspend the circidar paj't of their web in an 
open space : Also some remarks on the Food of 
Spiders, c^c. 
By Mark Watt, Esq. M. W. S. 
(Read 6th February 1830.; 
It was in consequence of observing it stated in the first 
edition of Kirby and Spence's Introduction to Entomo- 
logy, that it was not known how the garden or geometric 
spider attached the long lines which supported its web to 
two upright bodies at various distances from each other, 
and at a considerable elevation above the surface of the 
ground, that I made a number of experiments to ascertain 
how this was accomplished, and the result of these experi- 
ments was published in a short paper, in April 1817, in Dr 
Thomson's Annals of Philosophy 
The observations I have since made confirm what I then 
expressed, viz. that it is quite indubitable that the geo- 
metric spider has the power, either in a room or in the 
open air, when the atmosphere is calm, of throwing out its 
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