IMPROVED HYGROMETER, Q\$ 



£old loop to tbe Jirst interval of the screw, on the axis, 

 counting as before from tbe dial plate, (which is to fjfe 

 placed to tbe left band) and the index to 109, or zero. The 

 hygrometer must now be suffered to cool gradually, during 

 which, if the atmosphere be in a mean state of moisture, 

 the index will make four or rive revolutions; the oobeena 

 hooloo is then to be continually wetted with a hair pencil 

 and water, till the index is again perfectly steady. This 

 will require some time, as it moves very slowly when within 

 a few degrees of extreme moisture. The degree at which 

 the index stands is now to be noted, and the number of t«- 

 tervals counted between the dial plate and the gold loop, 

 and this number prefixed to the observed degrees will give 

 the extent of the scale. 



All observations made with this hygrometer are to be re* Reduction of 



duced to what they would have been had the scale consisted lhe obserT »* 



J . . tions to a 



of 1000 parts, or ten revolutions of the index. This is standard, 



most convenient, as it facilitates the comparison of obser^ 

 vations made with different hygrometers. An example may 

 not be thought superfluous. Suppose the scale of the hy- 

 grometer to be 1145, or eleven intervals and forty-five parts; 

 and that at the time of observation, there are/our intervals 

 between the dial plate and gold loop, and 50 parts shown by 

 the index; this would be written 450. Then, as 1145 : 

 1000 : : 450 : 393 nearly, the number of degrees to be 

 registered* 



If two of these hygrometers, in which the extremes of 

 dryness and moisture are well determined, be compared to- 

 gether, they will seldom differ ten divisions from each other, 

 which is as near a coincidence as can be expected. 



The oobeena hooloo or andropogon contortus is found in 

 every part of the country, in the month of January, when 

 it should be gathered, and thoroughly dried in the sun, be- 

 fore it is used. 



This grass appears to be far superior to any other by* Sensibility and 

 groscopic substance, hitherto discovered. In the Ency- other advan- 

 clopsedia Britannica, the scale of Saussure's hygrometer [^£ s u ^£ 

 is said to consist of 400 degrees, or rather more than on* 

 revolution of the index ; the hygrometer here described 

 wakes eleven or twelve revolutions ; U possesses also the ad* 



vantage: 



