213F DILATATION OF THE GASES. 



the firft. Thefe refults are evidently conlradi&ory ; but La- 

 hire not fufpecling any error, concluded that it muft be ne- 

 ceffarily allowed that the nature of air was yet undifcovered. 

 Lahire objects " Lahire, in order to give a reafon for the difference between 

 ments of Nuguet *" s refults and thofe of Nuguet, a difference much too great 

 on account of not to be owing to fome foreign caufe, remarked, that Nuguet 

 •water. j ia( j j e f t f ome wa i er j n hi s apparatus ; and from hence he 



judged that it might be this water, as it changed to vapor, 

 and expelled a portion of the air enclofed in the bottle, had 

 prefented fo great a dilatation. He was entirely confirmed in 

 his opinion by the refult of an experiment made in Nuguet's 

 method, a little Water being left in the bottle; for he found 

 that the volume of air dilated from the degree of temperate 

 to that of boiling water, and the primitive volume was as 35 

 and a half to 1. {Mem. de IJAmd. 1706.) 

 Stancari alfo ob- At the fame time M. Stancari of Bologne proved, that water 

 ftuence of water. at an e ^ evatec l temperature augmented the volume of air. To 

 thefe two philofophers then is owing the knowledge of the in- 

 fluence of water on the dilatation of atmofpheric air ; but al- 

 though they placed it by their experiments in the clearefl 

 light, it has been fince generally mifconceived. The great 

 variations in the refults of philofophers on the dilatation of 

 gafes, may likewife be attributed to the little attention that 

 has been paid to this influence. 

 The dilatations It is known that elevations in the atmofphere are given by 

 of air are of con- ^ e logarithms of the correfpondent heights of the barometric 

 rometrical ad- column. If the denflty of the air were always the fame, it 

 measurements, would be eafy to determine the height of one place above any 

 other known place by barometrical obfervation. Whence it 

 becomes of importance to diftinguifh the caufes that may in- 

 ildence the denfity of the air, in order (o make the neceffary 

 corrections in the heights given by the barometer. 

 Delucon theba- Deluc, who has thrown fuch great light on this branch of 

 Jurymen™*" philofophy, difcovered that heat was one of the caufes. That 

 he might well diftinguifh its effefts, he firft fought the tem- 

 perature at which the logarithms give the heights without 

 correction, and he found by comparing feveral obfervations 

 made in fituations whole heights he had exaclly determined. 

 Temperature of tnat tms ta ^ es P^ ace at tne temperature of 1 6° £ of the thermo- 

 which the logs, meter divided into 80 part*, which he calls the fixed tempe* 

 * lTC thc helBhu rature. To correct the effects of heat above and below this 



fixe4 

 4 



