Density, and Temperature of Gases. 



165 



must be read with certainty, other precautions presented them- 

 selves; for instance, the stopcock, it was found, must not be 

 opened and shut with the fingers, but a long wooden key must 

 be applied for that purpose ; and, again, the chamber containing 

 the exterior thermometer must be attached to the nozle by a 

 wooden adapter, and must be at the temperature required when 

 put in its place, and the jet must immediately take place. By 

 employing these methods and others which will readily suggest 

 themselves to an experimenter, the limits between which the 

 temperature of the jet must lie were gradually narrowed for 

 changes of density of about three atmospheres and two atmo- 

 spheres to that of one atmosphere, or for rarefactions two and 

 one. 



The figure represents the essential parts of the apparatus 

 which I have used. 







■ 



f L ^i^h 





