of a New Hygrometer. 



103 



invariably corresponded* to the temperature of the moist- 

 ened bulb when reduced to its lowest limits by means of a 

 strong current of air ; the local air immediately in contact 

 with the wet bulb becoming saturated before the utmost 

 limits of cold has been attained, and thus, preventing me- 

 chanically the contact of the surrounding atmosphere with 

 the bulb; by which means the utmost limits of refrigeration 

 are impeded, which air at a certain dryness would ensure, 

 did not this mechanical impediment prevent it. 



The experiments which I gave in my last paper prove, 

 that for each degree of humidity, the temperature of the 

 moistened bulb can only be lowered a certain limit, and 

 the constancy of this process, at every degree of humidity 

 will be seen in the following table : 

 Table of corrections, to be made use of in ascertaining the 



dew-point by means of the wet bulb hygrometer. 

 When the instrument is free from a strong current of air, 

 the number opposite to the degree of dryness is to be 

 added to that degree, which will then show the utmost 

 limits of refrigeration under those circumstances. 



• I think it right to state that in the preceding experiments the variations for the 

 force of vapour amount only to — '00112 in the 1st. Experiment, to -\- '00358 in 

 the second, and to + '00442 in the third ; which are too trifling to affect the com- 

 parison, and probably are to be attributed to errors in making the observationa. 



