116 THE MICROSCOPE AND ITS LESSONS. 



life, so derived, is intended as a protection from the 

 destructive influence of the world, preserving around him 

 who will receive it the atmosphere of heaven. 



I have told you how the spider tests the strength of 

 its rope before trusting its body upon it : another thought 

 here affords a good text for a homely lesson ; but how 

 does it know that such extreme tenuity is sufficient to 

 sustain its own weight ? 



To ascertain the strength of a rope, we more advanced 

 animals, who once upon a time, some a3ons of ages ago, 

 were "not human " * (!) multiply its circumference in 

 inches by itself, and the fifth part of the product will 

 express the number, say of tons, the rope will carry. For 

 example, if the rope be six inches in circumference 

 6x6 = 36 the fifth of which is 71 ; we thus ascer- 

 tain a rope of six inches in circumference will sustain 

 a weight of seven tons and a quarter. It were a curious 

 calculation to ascertain whether this law applies to the 

 finest home-made thread in the world, and whether the 

 line placed in the elaborate scale of an analytical chemist, 

 which will tell the weight of a human hair, would corre- 

 spond relatively with the weight of the creature who 

 made it. 



To form some idea of the circumference of a spider's 

 web, let me tell you that in some species, which are not 

 larger than a grain of sand, so very finely drawn are the 

 lines, that four millions have been reckoned as not 

 exceeding the circumference of a human hair; and yet 

 this extremely fine rope is a compound of so many smaller 

 threads, that in the six spinnerets of one full-grown spider 

 one thousand in each have been counted, from which the 

 liquid matter has been thrown out for the purpose of 

 making the curious net with which the clever workman 

 * According to some jnodern lights. 



