194 IN NATURE'S WAYS 



itself on tip-toe, and from its spinneret emits a silken 

 thread. This floats out on the air-current horizontally 

 a thread so fine that we can only see it when wet 

 and in sunlight. The spiders cling fast to their points 

 of vantage until the air-currents cause the threads to 

 begin to pull they will float, of course, on the very 

 softest breath of air. The threads pull, and then each 

 little spider vaults into space. 



They can sail only where the air carries them. 

 They may rise perhaps several hundred feet high ; 

 they may go too high, or perhaps too far, being 

 sometimes borne out to sea. But as they go they can 

 set more sail if they please, by emitting more silk, or 

 perhaps they withdraw part of the parachute until 

 they begin to sink to earth. 



Blind Instincts 



" Birds in general are wise in their choice of situation [when nest- 

 ing], but in this neighbourhood, every summer, is seen a strong 

 proof to the contrary, at an house without eaves, in an exposed 

 district, where some martins build, year by year, in the corners of 

 the windows. 



But as the corners of these windows (which face to the south-east 

 and south-west) are too shallow, the nests are washed down every 

 hard rain ; and yet these birds drudge on to no purpose, from summer 

 to summer, without changing their aspect or house. 



It is a piteous sight to see them labouring when half their nest is 

 washed away. 



Thus is instinct a most wonderfully unequal faculty; in some 

 instances so much above reason ; in other respects, so far below it I " 



