188 Prof. J. Le Conte on the Influence of 



The experiments of the latter show that rarefaction produces 

 striking alterations in the size and character of the flame, but do 

 not touch the question of the relative rate of burning under 

 difterent pressures : they test the comparative combustibiliti/ of 

 different bodies, rather than the rapidity of consumption oi& given 

 body under various degrees of rarefaction. Nevertheless Davy 

 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." Speaking 

 of the phaenomena 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 acting 

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

 would have been by an addition of one-fifth of oxygen." Again, 

 he says, "But by compression, there can be no doubt the heat 

 of flames from pure supporters and combustible matter may be 

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

 in the case of air he does not think the efi'ect would be so great. 

 Ina,smuch 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 oxidation, 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 most 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 65i 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 cofi'erdams, in such quantity 

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

 For this purpose, M. Triger employed large sheet-ii'on cylinders, 

 about 3'39 feet in interior diameter, securely closed at the top, 

 in which, by means of a condensing-pump incessantly worked 

 by a steam-engine, air was condensed to an amount sufficient to 

 counteract the external hydi'ostatic pressure. The ingenious con- 

 trivance fully justified the expectations of the engineer; but the 

 workmen were thus compelled to labour in air condensed under 

 a pressure of about three atmospheres. Among other curious 

 results of this state of things, noticed by M. Triger, were the 



