280 l^lk Manufacture. 



the light will not be reflected ; and, consequently, a thread thus 

 compounded cannot equal in lustre a solid thread. It is another 

 great disadvantage of the spider's silk, that it cannot be wound 

 off the ball like that of the silkworm, but must necessarily be card- 

 ed ; and therefore its evenness, which contributes so materially to 

 its lustre, is destroyed. That this effect was in reality produced, 

 is further confirmed by the testimony of M. le Hire, who, when 

 the stockings of M. Bon were presented to the Royal Academy, 

 immediately noticed their want of lustre. 



' Another objection urged by M. Reaumur against the rearing of 

 spiders was the small quantity as well as deficient quality of the 

 silk they produce. In making a comparison in this respect be- 

 tween them and the silkworm, extreme cases were taken, that the 

 conclusion might be rendered more striking. " The largest co- 

 coons," said this naturalist, "weigh four and the smaller three 

 grains each ; spiders' bags do not weigh above one grain each, 

 and, after being cleared of their dust, have lost two thirds of this 

 weight." He calculated, therefore, that the work of twelve spi- 

 ders only equals that of one silkworm ; and that a pound of silk 

 would require for its production 27,G48 insects. But as the bags 

 are wholly the work of the females, who spin them as a deposit 

 for their eggs, it follows that 55,296 spiders must be reared to 

 yield one pound of silk : yet even this will be obtained from only 

 the best spiders, those large ones ordinarily seen in gardens, ^c, 

 yielding not more than a twelfth part the silk of the others. The 

 work of 280 of these would, therefore, not yield more silk than 

 the produce of one industrious silkworm, and 663,552 of them 

 would furnish only one pound of silk ! This latter calculation is 

 however decidedly erroneous in its several steps, and appears 

 rather to be a flight of the imagination than the result of sober in- 

 duction. The advantages of the culture of silk from the silkworm, 

 when compared with its production from spiders, are so prodi- 

 gious, and at the same time so evident, that to prove the futility 

 of M. Bon's scheme needed not the aid of exaggeration. 



* Human ingenuity has been somewhat more successfully exer- 

 cised in seeking, many feet below the surface of the ocean, for 

 slender filaments, the produce of an animal irv almost a vegetative 

 state of existence. 



' The pinna belongs, like the common edible muscle, to the or- 

 der of the Vermes testacea. The animal is a limax, its shell is bi- 

 valve, fragile, and furnished with a beard ; the valves hinge with- 

 out a tooth. The pinna does not fasten itself to rocks in the same 

 situation as the muscle, but sticks its sharp end into the mud or 

 sand, while the rest of the .shell remains at liberty to open in the 



