On extracting Vinegar from Wood. 439 



From the above experiments, we see that the same body may 

 Ik- made to produce either positive or negative electricity at 

 Pleasure; and that 7«e/«///c bodies, like viticH^us and resinous 

 .ones, vviil by similar treatment, like them, produce smn'.ar states 



of electricity. , , , , , i 



From which I think it is l)nt fair to concliule, that the classing 

 of bodies into electrics and »o'i-electrics, as well as into positive 

 mul negative electrics, is founded in error, and at variance witli 



fisiicriments. , 



V s —The silk which I used was wrapped several times roiin'l 

 a thin board about one foot three inches long, and five inches 

 wide, with a handle similar to a battledore. 



I am, sir, voars, &."c. 

 Dorset-treet, June 14, 1S18. .1 . i -ai . -. 



LXXVII. Process prnctisffl in the EstuLlishment of Synut- snr 

 Seine to extract Finegar or Jkttic Acid from fVood. xjij 

 M. P. L. Dui'UV'iRiiN*. 



At one end of a larsre buiUlin.e; calculated for the purpose, 

 are four furnaces, adaptc.l to receive large retorts, the lower parts 

 of wh'ch are made in cast iron, and the rest m strong iron plates: 

 at a small distance from the bottom of these retorts is the open- 

 jncr of a copper pipe of three inches diameter, which rises through 

 the metal of the retort, and widens like a tunnel ;.t the upper 

 end • a copper cylinder eight or nine inches wide, and eigliteen 

 or t^Wntv long, is fixed to this tunnel, passing out of the budd- 

 5no- is bent downwards, and is plunged into a large tub full of 

 water ' which is constantly renewed : from this it discharges 

 itself into a condenser, to which are adapted on oi.e side a small 

 cock to carry off licpiids, and on the other a cylmder of about the 

 ■^anie bore as the one mentioned above, and which rises verti- 

 cally, then turns down and enters into the building, where it is 

 again bent, and opens at the hearth of the furnace. 



This apparatus being arranged, the retorts are filled with 

 nieces of wood which have been cut a year, and which must be 

 chosen straight and long, and about as large as the wrist : these 

 pieces are arranged in the retort with order. \Vhen the retort 

 is hill rtis covered with its lid, which is fastened on by means ot 

 screws • it is then luted carefully with clay, and by means of a 

 crane two men raise it up and place it in its furnace : over this 

 is put a covering of masonry of considerable weight; tlie cy- 

 linder is fitted to the retort, and the fire is lighted. 

 • From ihc Journal rie Pliarmack'. 



E e 4 T^e 



