1819.] American Mode of increasing Heat. 20? 



cistern was void of water, and that when water was placed in 

 the safety cell, it was enlarged, it requires also to be occa- 

 sionally replenished ; and I could not find that the small portion 

 driven by the retrogression of the flame into the reservoir was any 

 equivalent for the quantity supplied. When oil is made to sub- 

 stitute the water, it too disappears, the flame is not so intense, 

 and carbonaceous matter is found in contact with the escape 

 pipe; in both cases there is probably a partial decomposition; 

 hence an attenuation of intensity of flame. When oil is used, 

 carbonic oxide or carburetted hydrogen would certainly, by 

 mingling with the condensed oxygen and hydrogen, have this 

 direct tendency. 



You are aware that about two miles from Pietramala there is a 

 constant evolution of carburetted hydrogen, described so lono- 

 ago as 1776 by J. J. Ferber, and the following are his words : 

 '* On the sloping side of a hill towards the valley appear conti- 

 nual flames, which, being ever to be seen, have caused this hill 

 to be called Pietramala. The flaming place is covered with 

 earth, and loose separate lime, clay, and marl stones. It has 

 properly but six feet diameter, and the flames appear between 

 and upon the before-mentioned stones. The flames are exceed- 

 ingly clear and are yellowish-white as arising from burning oil. 

 They rise about two feet above the ground, give no mark of any 

 sulphureous acid, grow stronger after wet weather, and fainter in 

 a dry summer." These extracts are quoted to show that this 

 exhibition is not a new discovery. 



When I crossed the Apennines on mv journey to Florence, I 

 was naturally anxious to visit so curious a phenomenon. The 

 few experiments which I was enabled to make convinced me 

 that the flame was continued by a constant evolution of pure 

 carburetted hydrogen. The flame was only a few inches high, 

 the weather for some time before had been particularly dry, and 

 continued so for many days after ; when the breeze agitated the 

 flame, propelling it in a given direction, it exhibited that^'we blue 

 colour which appears when the bright flame of supercarburetted 

 hydrogen is acted upon by a current of air. By placing a small 

 glass bell over a confined portion of it, I obtained a quantity of 

 the gas, which burned with a yellowish-white flame in an inverted 

 sfcl, when ignited in contact with the atmosphere, and it 

 detonated violently when mixed with a due proportion of that 

 medium. W T hat particularly struck me was the remarkable 

 etherial ■smell which accompanied this extraordinary and perpe- 

 tual combustion. When I returned from the south of Italy, I 

 was desirous of revisiting this ' volcanello ' (as the natives call it), 

 and examine the hygrometric state of the atmosphere in refer- 

 ence to it, as I had done before. This anticipated pleasure, 

 however, it was not my good fortune to realize. The snow was 

 three and four feet deep even on the road, and our " vetturino" 

 was necessitated to effect his progress by harnessing four oxen 



