OF WASHINGTON. 387 



web ; in other places it rolled up into a ball. To me it seemed 

 like the down of silk-weed (Asclepias), or the fibre of some such 

 plant. You may have the same thing where you are, for it seems 

 to have been general about here. I might have examined it with 

 the microscope, but there is something out of fix about it, or I 

 have forgotten how to handle it. This is something for your nat 

 uralists and microscopists." 



The bulky sample from Florida this year allowed me to test it 

 more carefully and I have been convinced by the thorough micro 

 scopical and chemical examination that it is a product of animal 

 origin. This microscopic examination shows an entire absence 

 of structure : fine slender threads rather spirally contracted ap 

 pearing solid as glass rods under the microscope ; not hollow, 

 not the slightest appearance of a cell-wall, which would indicate 

 the vegetable nature. Water contracts the specimen, the spirals 

 being shortened and the fibres rendered more opaque. 



The chemical examination showed all the characters of animal 

 substance ; it burns readily in a flame, so cannot be of mineral 

 origin. Potassic hydrate coagulates and nearly destroys the 

 specimen. Iodine alone turns it a yellow-brown color. Acetic 

 acid decidedly contracts it. Zinc chloride partially destroys it and 

 does not produce the violet color which would result were the 

 substance cellulose ; it is also rendered more opaque by this 

 reagent. Nitric acid coagulates it, leaving only a small sediment 

 or burned residue. Nitric acid followed by iodine simply gives 

 the brown color of the iodine to the residue ; were the substance 

 of vegetable origin it would take a pronounced blue color with 

 these two reagents. Phosphoric acid and iodine give the same 

 color as the preceding ; nothing of the appearance of blue. Sul 

 phuric acid and iodine produce the same effect, though possibly 

 not so deep a brown as either of the former ; they do not give 

 the blue color which indicates a vegetable origin. Hydrochloric 

 acid destroys the specimen entirely. Zinc chloride and iodine 

 give a deeper yellow color, almost a dark brown, rather than 

 blue. It is destroyed or coagulated by hydrochloric acid, nitric 

 acid, potassic hydrate, and by Schultz's solution. Not one of 

 these chemical reagents destroys vegetable fibres. 



The length hundreds of yards and the minuteness of indi 

 vidual threads, warrant the opinion that we have before us the 

 product of the spinning glands of a spider, or rather thousands of 

 spiders. 



You know that young spiders are in the habit of availing them 

 selves of their spinning product to migrate from their birthplace 

 by floating through the air to very remote localities ; if rain 

 should moisten these weavings, they mat together, and thus 

 become too heavy to float, and fall to the ground. 



The species of spider which makes these weavings is of course 



