On certain Products obtained in the Distillation of Wood. 203 



by the hypothesis of Volta. This philosopher analyses the elec- 

 tric fluid into two elements : the one, called electric matter, can- 

 not pass through the glass ; the other, called deferent fluid, passes 

 with ease. JNIr. De Luc subjoins : " so far this system might 

 appear only an hypothesis to Mr. Donovan, as he does not know 

 the work to which I refer." I must coiifess that to me the whole 

 has a very hypothetical appearance, but I am willing to admit 

 my ignorance of the above-mentioned work as the cause. There 

 is not, however, any hj'pothesis in the simple experiment which 

 was detailed in my former paper. A thin flask with a neck many 

 inches long was half filled with mercury, and coated on the 

 outside to the same height with foil. By means of a moveable 

 wire, an electric charge was thrown in ; the wire was drawn out, 

 and the neck was hermetically sealed. After a length of time 

 the sealing of the neck was cut off; the wire was plunged into 

 the mercury; but not the slightest commotion was perceived by 

 the hand, although the original charge was capable of giving a 

 violent shock. Thus I had encompassed a quantity of electricity 

 on all sides by glass ; after a certain time I found that the glass 

 contained none : — What should I conclude, but that it escaped ? 

 Were Mr. De Luc to repeat this experiment, he would certainly 

 consider my inference natural. 



Many more observations might be made, but these are all that 

 I consider necessary to offer for Mr. De Luc's consideration. 

 The object of my former paper was not to defend any hypothesis, 

 but, on the contrary, to show that we are deceived when we sup- 

 pose ourselves possessed of any knovvledge of the electric fluid 

 beyond the perception of its sensible effects. The only mode of 

 inviting truth is to remove the barriers which oppose its progress. 

 I am persuaded that there woidd be no one more willing than 

 Mr. De Luc to lend his assistance to the acquirement of so dfe- 

 sirable an object, 



I am, sir, &c. &c. 

 Dublin, March 10, 1815. M. DoNOVAN. 



XXXVIIL On certain Products obtained in the Distillation of 

 Wood, with some Account of bituminoits Substances, and Re- 

 marks on Coal. By J. MacCulloch, M.D. F.L.S. Chemist 

 to the Ordnance, and Lecturer on Chemistry at the Royal 

 Military Academy at Woolwich* . 



It is well known that when wood and other vegetable substances 

 arc submitted t-i destructive distillation, there is produced, among 

 other matters, a black dense fluid resembling molasses or com- 



• From the Geological Transactions, vol. ii. 



mott 



