Si On preventing the hijurious Effeets resulting from the 



at the top like a common chimney, and making an iipriglit vent 

 of 50 feet, the whole length of the flue being 950 feet; the bot- 

 tom of the flue rises about an inch in every 34 feet, upon the 

 principle that a regular ascent was necessary to indulge the 

 propensity of the hvdrogen to ascend, and thus facilitate its 

 passage forward, whilst it was at the same time desirable to keep 

 the smoke confined to a passage as nearly horizontal as was 

 consistent with that principle; ibr, in a former experiment, it 

 had been found that, from the want of this caution, and in con- 

 sequence of some descent in the flue, the hydrogen accumu- 

 lated in it so as to burn like gas on the application of a light, 

 and on one occasion to cause a violent ex])losion. 



In the first experiment with the new flues a ton of copper 

 was placed in the ftnuiace, M'hen at a proper heat, and the 

 process of calcining commenced: the following account is ex- 

 tracted from the letter of the gentleman who repoits upon it: 



" The smoke issuing irom the vent was perceptible only to a 

 good eye looking against a wood behind it; two persons ascended 

 to the top of the perjiendicular stack, whilst a workman stirred 

 the ore in the furnace: whilst this was doing, two observers sat 

 on the edge of the stack on the lee side, so that all the smoke 

 which issued must pass over their faces; and they state that they 

 found no kind of inconveniences when seated on the mouth of 

 the chinmey." The reporter says, " Whilst I stood by the 

 furnace I could perceive a small issue of smoke, which appeared 

 to Jrover for an instant at the mouth of the stack, but was dis- 

 sipated very soon after it had entered the atmosphere. I went 

 up to the stack and into it by the door, there I found a mix- 

 ture of smoke and hydrogen gas, smelling like common smoke; 

 but I inhaled it repeatedly without experiencing any of those 

 distressing sensations which always affect me when I inhale 

 copper smoke, and to which you were once witness, as we 

 walked by the crown works on a day when, the smoke being 

 remarkably low, it was impossible to avoid it. I innnediately 

 went into the garden and procured a common plant in a pot 

 in full vegetation; this I had placed on the summit of the stack, 

 and the superintendant tells me this evening, that it does not 

 yet appear at all affi?cted; indeed, he declares it impossible that 

 it should be; he says he has no doubt remaining on the subject, 

 * the thing is accomplished, and nearly all the smoke which 

 does escape is combustible;' he adds, 'it is evident diat 950 

 feet of such flues are sufficient to destroy all the noxious pro- 

 perties of the copper works.' " 



This experiment was made on the 23d of March 1822. On 

 the 25th, the reporter proceeds as follows : — " On opening the 

 ffues this morning, the first and second were found charged 



with 



