322 J. LeConte on the Injluence of Solar Light on Comhisfion. 



ferent bodies, rather than the rapidity of consnmption of a given 

 body under various degrees of rarefaction. Nevertheless, Savj 

 informs us, that he determined from actual experiment, that the 

 amount of heat developed in a given time by combustion, is slowly 

 diminished by rarefaction ; '' the diminution of the cooling power 

 of the nitrogen, being apparently in a higher ratio than the dimi- 

 nution of the heating powers of the burning bodies," ^-^-- -■^'^ 

 of the phenomena of combustion in condensed air^ he says, "I 

 ascertained, however, that both the light and heat of the flames 

 of the taper, of sulphur and hydrogen, were increased by acticg 

 on them by air condensed four times ; but not more than they 

 would have been by an addition of \ of oxygen." Again, he 

 says, ''But by compression, there can be no doubt, the heat of 

 flames from jpz^re supporters and combustible matter may he 

 greatly increased, probably in the ratio of their compression:" — 

 in the case of air he does not think the effect would be so great. 

 Inasmuch as the quantity of heat developed in a given time by 

 the burning of a given substance^ is known to be a measure of the 

 amount of matter undergoing oxydation, we are justified in the 

 inference, that the foregoing results of Sir H. Davy's experi- 

 ments, show that the rate of combustion was retarded by the 

 rarefaction and accelerated by the condensation of the air. 



The mo^t satisfactory results in relation to the influence of 

 condensed air on the process of combustion, are those incidentally 

 furnished about sixteen years ago, by M. Triger, a French civil 

 engineer, during the operations necessary for working a bed of 

 coal lying under the alluvium bordering the river Loire, near 

 Languin in the department of Maine-et- Loire. In traversing an 

 overlying stratum of quicksand from 59 to Qb^ feet thick, he 

 found it requisite to devise some means of excluding the semi- 

 fluid quicksand and water^ which found their way under every 

 arrangement analogous to ordinary cofferdams^ in such quantity 

 as to defy all pumping operations intended to keep them dry ^ 

 For this purpose, M, Triger employed large sheet-iron cylinders, 

 about 3*39 feet in interior diameter, securely closed at the top, ii^ 

 which,— by means of a condensing pump incessantly worked by 

 a steam-engine,— air was condensecl to an amount sufficient to 

 counteract the external hydrostatic pressure. The ingenious con- 

 trivance fully justified the expectations of the engineer; but tne 

 w^orkraen were thus compelled to labor in air condensed under a 

 pressure of about three atmospheres. Among other curious re- 

 sults of this state of things noticed by M. Triger, were the re- 

 markable effects of condensed air on combustion. Much annoy- 

 ance was at first experienced from the rapid cornhnstion oi tne 

 candles; which was only obviated by substituting flax for cotton 

 threads in the wicks.* Similar phenomena were observed a le^v 



* ^^■^,Cnmpte3Rendu8,Tomel3,p.884,et.eq., Paris, m]. Also, Mnaje^ 

 de Chimie et de Physique, 3d Swcs, Tome 3. p. 2S4, et seq., Pans. 1841.— ^^ 



* 



