244 On Oxalic Acid. 



smallest have the same properties, and the thread may be 

 seen to unfold with a good glass. By what means these 

 threads are separated at the instant they are drawn from the 

 spider's body, I am at a loss to determine, and by what kind 

 of construction the aperture from whence they are drawn is 

 contrived to spin a thread of a gummy consistence, either 

 single or double, at the pleasure of the spider, is equally 

 mysterious. 



The spider, for some reason or other, is generally looked 

 upon with abhorrence, and some have declared them to be 

 poisonous, but the fact is otherwise ; they are perfectly in- 

 nocent, which could be easily proved, and they are a very 

 ingenious and wonderful Utile insect, highly deserving the 

 attention of the curious. When I say they are not veno- 

 mous, I speak only of our English spiders ; for notwith- 

 standing their dexterity in killing a fly, there is, I believe, 

 no doubt as to the means they use for that purpose, being 

 commonly done by incisions made with their formidable 

 forceps, and then sucking their blood. 



There are many other very curious observations which 

 mioht be made, peculiar to the spider, and which I may 

 at a future period trouble you to insert in your valuable 

 Magazine. I am, sir, yours, &c, 



R. Teed. 



XLVI. On Oxalic Acid. Bij Thomas Thomson, M.D. 

 F.R.S. Ed., Communicated hj Charles Hatchett, 

 Esq.y F.R.S. 



[Continued from p. 111.] 



III. Decomposition of the Oxalates. 



I.VVhen oxalic acid, in the state of crystals, is exposed 

 to heat, it is only partially acted upon, a considerable por- 

 tion escaping without alteration ; but when an alkaline or 

 earthy oxalate is heated, the acid remains fixed till it under- 

 goes complete decomposition. The new substances into 

 which the acid is converted, as far as my experience goes, 

 are always the same, what oxalate soever we employ. They 



are 



