136 Dauiell on a new Hygrometer. 



Very shortly after the commencement it was observed that 

 the wind died away to a calm, and the smoke drove from the 

 S.W., with a great tendency to beat down. The clouds in- 

 creased rapidly round the sun, assuming the form of cirro- 

 cumuli, the haze at the same time became more dense. They 

 continued to increase, and at intervals totally obscured the view, 

 till about fifty minutes past one, when they began tp dissolve, 

 and at 20 minutes past two the sun was again perfectly clear, 

 and remained so till the end. The barometer, as far as I could 

 judge, was unusually steady during the whole time. The ob- 

 servations were continued every quarter of an hour, as follow : 



Clock. Thermometer. Dew Point. 



121 67^ 51 



12| 67| 51 



1 66 ...... 52 



li 65 51 



IJ 64 ...... 50 



1| 64 50 



2 63^ 53 , 



2i 63 52 



2^ 63 51 



2f 63i 52 



3 ... .. 64i 52 



H ...... ^^ 52 



5 65 52 



Thus it appears that there was a depression of temperature 

 amounting to 5°, the maximum of which was 25 minutes, after 

 the greatest obscuration. There was also a sensible vacillation of 

 the point of precipitation ; but whether this, and the momentary 

 increase of the clouds, were occasioned by an accidental shift of 

 the wind, or whether all were dependent upon the change of 

 temperature, consequent to the obscurations of the sun's light, 

 may be matter of some doubt. The change of the wind was 

 permanent, and at eleven o'clock at night the constituent tem-* 



