SPIDERS. 345 



stream of air, or some subtle electric fluid, by which 

 she guides it as if by magic. 



A living writer (Mr. John Murray), whose learn- 

 ing and skill in conducting experiments give no lit- 

 tle weight to his opinions, has carried these views 

 considerably farther. " The aeronautic spider," he 

 says, " can propel its thread both horizontally and 

 vertically, and at all relative angles, in motionless 

 air, and in an atmosphere agitated by winds ; nay 

 more, the aerial traveller can even dart its thread, to 

 use a nautical phrase, in the ' wind's eye.' My opi- 

 nion and observations are based on many hundred ex- 

 periments The entire phenomena are elec- 

 trical. When a thread is propelled in a vertical 

 plane, it remains perpendicular to the horizontal 

 plane, always upright, and when others are projected 

 at angles more or less inclined, their direction is in- 

 variably preserved; the threads never intermingle, 

 and when a pencil of threads is propelled, it ever 

 presents the appearance of a divergent brush. These 

 are electrical phenomena, and cannot be explained 

 but on electrical principles." 



"In clear fine weather the air is invariably posi- 

 tive ; and it is precisely in such weather that the aero- 

 nautic spider makes its ascent most easily and ra- 

 pidly, whether it be in summer or in winter." " When 

 the air is weakly positive, the ascent of the spider 

 will be difficult, and its altitude extremely limited, 

 and the threads propelled will be but little elevated 

 above the horizontal plane. When negative electri- 

 city prevails, as in cloudy weather, or on the approach 

 of rain, and the index of De Saussure's hygrometer 

 rapidly advancing towards humidity, the spider is un- 

 able to ascend."* 



Mr. Murray had previously told us, that " when 



* Loudon's Mag. of Nat. Hist., vol. i. p, 322. 



