426 Of the Propagation of Heat . 



long, received the end of the tube of the thermometer 

 into a hole bored through its center or axis, and con- 

 fined the thermometer in its place, without the assistance 

 of any other apparatus. Through this stopple two 

 other small holes were bored, and lined with thin glass 

 tubes, as in the thermometer No. 3, opening a passage 

 into the cylinder, which holes were occasionally stopped 

 up with stopples of cork; but to prevent accidents, such 

 as I have before experienced from an explosion, great 

 care was taken not to press these stopples into their 

 places with any considerable force, that they might the 

 more easily be blown out by any considerable effort of 

 the confined air, or vapour. 



Though in this instrument the thermometer was not 

 altogether so steady in its place as in the thermometers 

 No. I, No. 2, and No. 3, the elasticity of the tube, and 

 the weight of the mercury in the bulb of the thermom- 

 eter, occasioning a small vibration or trembling of the 

 thermometer upon any sudden motion or jar ; yet I 

 preferred this method to the others, on account of the 

 lower part of this thermometer being entirely free, or 

 suspended in such a manner as not to touch, or have 

 any communication with, the lower part of the cylinder 

 or the globe ; for though the quantity of Heat received 

 by the tube of the thermometer at its contact with the 

 cylinder at its choaks, in the instruments No. i and 

 No. 2, or with the branches of the steel spring in No. 

 3, and from thence communicated to the bulb, must 

 have been exceedingly small ; yet I was desirous to 

 prevent even that, and every other possible cause of 

 error or inaccuracy. 



Does humidity augment the conducting power of 

 air ? 



