SCIENTIFIC TRACTS. 



NUMBER XI . 



EVAPORATION. 



THIS is a process which is continually going on around 

 us. The earth is alternately dried and replenished with 

 moisture, the streams shrink and grow again, vegeta- 

 tion at one time mourns the absence of her genial nour- 

 isher, and at another glows with renovated life and vigor ; 

 all these changes are the effect? of evaporation. Often 

 on one day the weather is fair and clear, and the sun 

 goes on ' rejoicing as a strong rmm to run a race.' The 

 next day, the face of the heaven is veiled in clouds, and 

 the drenching rain or chilling snow is rapidly descending. 

 In the morning, nature is smiling beneath the light of 

 day, and before the shades of evening have fallen upon 

 the landscape, the tempest has risen in its wrath, and the 

 thunder is echoing through the sky. What is the agent 

 that has produced this transformation 1 What is it, that 

 at one time forms the materials 'ibr the tempest, and at 

 another, creates the golden clouds that gather around the 

 path of the descending sun 1 It is evaporation. It is 

 this that dries the face of the ground in spring, gives the 

 beautiful greenness to the fields of summer, and prepares 

 the materials for the snows and storms of winter. 

 Scarcely less important are the effects of evaporation on 

 domestic economy. To the painter, the clothier, the 

 calico-printer, it is indispensable ; to those engaged in 

 the daily routine of domestic avocations, no less so. 

 They all rely upon it with implicit confidence, nor do 

 they rely in vain. For thousands of years it has been 

 employed, and still it performs its destined task, as faith- 



VOL. i. NO. xi. 23 



