294 SCIENCE FROM AN EASY CHAIR 



The threads produced by the hardening of the 

 tenacious fluid exuded by these various animals were 

 probably simply protective in origin. The curious cater- 

 pillar-like creature Peripatus spits out a viscid fluid when 

 it is disturbed, which hardens into threads, and hopelessly 

 entangles any small enemy -which may venture to attack 

 it. Threads of a poisonous nature are thrown out by 

 jelly-fishes, polyps, and sea anemones, and serve them 

 both as defence and as means of paralysing and capturing 

 prey. A later stage in the use of such threads is their 

 " felting " to form a case or tube (as in the sea anemone 

 called Cerianthus\ and so their application has gradually 

 developed to the formation of egg-cases, snares, and the 

 wonderful web of the geometric spider, and the countless 

 " flying-lines " of smaller spiders, which make up the 

 mysterious thing we call "gossamer." 



As to the limits of the tenuity of the threads of 

 gossamer there are no direct observations. Probably they 

 are often as fine as the Tr.^inyth or s^i^th of an inch in 

 diameter. The condensation of a very minute quantity 

 of moisture on gossamer threads and spiders' webs no 

 doubt helps to make them more readily visible to us in 

 October weather than they are in full summer, when such 

 moisture would not condense except in early morning or 

 at sunset. It seems strange that man should have been 

 unable to produce a thread so fine as that of the spider, 

 but this reproach has now been removed. Spun glass is 

 easily obtained Trnnrth of a inch in diameter ; but Mr. C. 

 V. Boys, F.R.S., has, by fusing quartz (rock-crystal) by the 

 oxy-hydrogen flame, and drawing it out by means of a 

 small arrow (a straw), discharged from a bow the near 

 end of the arrow being adherent to a fused droplet of 

 quartz which is held fast produced threads of great 

 strength and of extraordinary tenuity. The fineness can 

 be regulated by the rapidity with which the drawing is 



