TABLE OF DEW-POINT. 



183 



Th.e bulbs of both, tbermometers should be covered with a fold of 

 white silk or muslin, and pure water supplied to one of them from a 

 phial or other vessel placed near it, by a thread of floss sUk acting as a 

 siphon. The cover of the moistened bulb and the thread must be 

 renewed occasionally. — The above table is sufficiently accurate for all 

 practical purposes, but the true decreasing ratio is 2*33 for each degree 

 of depression indicated by the moistened thermometer,* '^, 



After having obtained by Mason's hygrometer, 1st, the temperature 

 of the air, as indicated by the dry thermometer, and, 2nd, the difference 



* To find the corresponding degree of Leslie's hygrometer, multiply the numher of 

 degrees of difference between the dry and moistened thermometers by 6. 



