446 Relations of Air, Heat, and Cold. 



caution being used, no accident happened, and the inhabi- 

 tants were not in the least *ncommo'Jed. 



The saaie disinfecting apparatus has been employed in 

 the works going on in iheRiieMontmarlre. The quarrying 

 for the sewers and drains has been carried down to the pits 

 which were dug in this part of Paris in the reigns of 

 Charles VI. and Louis XIII. The filth with which these 

 ancient cemeteries was filled, exhaled an infectious and in- 

 supportable odour ; but the process of Guyton being speedily 

 applied, no accident happened. 



LXVIII. On the Relatvms of Air to Beat, Cold, and Mois- 

 ture, and the jSleam of ascertaining their reciprocal Ac- 

 tion. By J. Lkplie, E^q. F.ll.S.E. Professor of Ma- 

 thtmatics in the University of Edinbjirgh*. 



X. HE various phaenomena of heat are most easily con- 

 ceived by referring them to the operation of a peculiar fluid 

 possessing extreme activity, and diflfused through all bodies." 

 It constantly endeavours to maintain its equilibrium or 

 equal diffusion among bodies, and its accumulation in any 

 subsilance is generally marked by a corresponding expan- 

 sion. The extent of this expansion in different bodies 

 ▼aries as they transmit heat more or less rapidly, or have 

 divers conducting powers. Air is found, in like circum- 

 stances, to expand five times more than alcohol, yo times 

 more than mercur\-, 160 times n)ore than platina, and 

 even 580 times more than glass. The thermometer is an 

 instrument contrived to measure its own expansions ; but 

 it can mark only the heat of its own bulb, as affected by 

 external communication, and any further inferences drawn 

 from its different indications are merely the result of some 

 process of reasoning f. 



" Heat combines with different substances in proportions 

 widely varied, and depending in each on its peculiar and 

 intimate structure. In general, it is more copious in liquids 

 than in solids, and in the aeriform fluids than in liquids. 

 But still the allotment among the different bodies, appears 

 to be as various as their distmctive properties. Under si- 

 n)ilar circumstances, hydrogen gas will hold or absorb ten 

 times as much heat, as an equal mass of atmospheric air ; 

 water twice as much as olive oil, and three times as much 



* Abstracfed from " A View of Experiments and Instruments depending 

 •11 the Relations of Air to Heat and Moisture." 



\ See Tilloch's Essay on Caloric, Phil. Mag. vol. viii. 



as 



