WIND- VANE SKY. 27 



1. A light breeze which moves the foliage, and sometimes fans 

 the face. 



2. A wind which moves the branches of the trees, somewhat 

 retards walking, and causes more or less of a slight rustling 

 sound in the open air. 



3. A wind which causes strong boughs and entire trees to 

 rock, makes walking against it difficult; which causes a stronger 

 rustling sound to be heard, and which often blows in gusts, and 

 carries light bodies up into the air. 



4. A storm-wind, during which the trees are in constant mo- 

 tion ; branches and boughs covered with foliage are broken off, 

 and in a violent stcrra sometimes even entire trees are broken, 

 or uprooted; leaves, dust, &c., are continually borne up and car- 

 ried far away ; during which time there is an uninterrupted loud 

 rustling sound, with strong gusts; walking windward is ex- 

 tremely difficult, and now and then chimneys, fences, &c., are 

 thrown down, windows broken in, &c. 



These degrees correspond nearly to the following numbers of 

 Beaufort's scale, which is generally used among seamen : 



1. the same as 1. Light breeze, ] 

 . 2. " " " 4. Moderate breeze, I of Beaufort's 



3. " " " 8. A fresh gale, scale. 



4. " " " 11. A storm-wind, J 



[The force of the wind is now estimated and registered ac- 

 cording to the direction on the blank forms.] 



SKY. 



The blue color of the sky has an intimate connection with the 

 hygrometrical state and the electrical tension of the air; it may 

 be noted by the expressions, dark, light, and grayish. 



Haze and dry mist. The transparency of the air is often dis- 

 turbed by a kind of vapor, which gives a whitish tint to the sky 

 and dims the rays of the sun. This phenomenon, known in 

 Europe under different names, appears frequently after long 

 droughts; in this country it seems to characterize the Indian 

 summer. In Europe, and elsewhere, an intensely dry mist, which 

 is, probably, a different phenomenon, sometimes follows great 

 earthquakes or volcanic eruptions. The observer will carefully 



