370 Account of some Discoveries in Chemical Philosophy. 
luminating nor the chemical rays produce heat, and they 
are, consequently, incapable of exciting combustion.” 
* To the exhibition, however, of these phenomena in 
combustion the presence of oxygen is necessary; for the 
calorific rays do not excite combustion in vacuo, nor in any 
gas deprived of oxygen, even when the most inflammable 
substance is employed. The very same condition is re- 
quired for the excitation of electricity. Colonel Haldane 
observed, that, when the Voltaic pile was placed in vacuo, 
its action immediately ceased ; that in nitrogen gas it did 
not even commence ; while in oxygen gas, or in atmospheric 
air, it acted with energy, and the oxygen disappeared. These 
facts were confirmed by Mr. Davy, who found that, in gas 
devoid of oxygen, no Galvanic electricity could be excited 5 
but it was more or less abundantly developed, when oxygen 
gas was present*.” Hence, what has hitherto been called 
positive electricity, is unquestionably the elementary or im- 
pancesahle part of oxygen gas—one of the elements of com- 
ustion. 
Sir Humphry Davy found great difficulty in breathing _ 
hydrogen gas for so long a time as half a minute. It pro- 
duced uneasy feelings in the chest, and momentary loss of 
muscular power, and sometimes a transient giddiness f. 
And some persons have experienced giddiness, loss of 
muscular motion, and fainting, when standing near @ 
powerful electric machine while in action f. 
When an electric is strongly excited, it causes the sensa~ 
tion of the spider’s web upon the face brought near it§.., 
And in coal mines highly charged with hydrogen gas, the 
workmen always experience the same sensation. 
Now from these facts it appears, that when a portion of 
air is charged with what is called negative electricity, it is, 
in fact, charged with hydrogen gas. 
On the elementary principles of oxygen and hydrogen gases, 
called positive and negative electricity. 
When a Leyden jar is discharged through the air, @ 
spark is produced which sets certain bodies on fire. That 
a charged jar contaius the two elements of combustion, 
cannot be disputed with any degree of reason, since com-— 
° oO 
bustion has been produced by these elements thousands of 
times, without any other means whatever, except some pon-~ 
derable matter for them to act upon. 
* Ellis on Atmospheric Air, p. 188, + Thomson’s Ghemistry, vol. i. p.34. 
¢ Yatman on the Elgctrie Fluid. § Cavallo’s Electricity, p. 408. ; 
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