THE SMITHSONIAN INSTITUTION. 233 



The manner in whicli the wind turns, or rather the order in which 

 the winds sncceed each other in the conrse of the day, must he watched 

 very carefully. It will he seen that they commonly follow in regular 

 order ; they pass from the east by the south to the west, and from the 

 west, by the north, to the east. Nevertheless, they sometimes go hack 

 in the opposite direction, particularly during storms. A little mem- 

 orandum, summing up in a few words at the end of each day this 

 course of the wind, together with the hour's of the wind's changes, 

 is very valuable. It may be entered in the column of remarks. 



The force of the wind must be estimated as nearly as possible ac- 

 cording to the following degrees : 



0. A perfect calm. 



The sim])le initial letter of the wind, for instance N". (north,) indi- 

 cating its direction without any number, means a slight movement of 

 the air hardly to be called a wind, and only just sufficient to allow an 

 estimate of its direction. 



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 motion ; 

 branches and boughs covered with foliage are broken off, and in a 

 violent storm sometimes even entire trees are broken^ or uprooted ; 

 leaves, dust, &c., are continually borne up and carried far away; 

 during which there is an uninterrupted loud rustling sound, with 

 strong gusts ; walking windward is extremely difficult, and now and 

 then chimneys, fences^ &c., are thrown down, windows broken in, &c. 



These degrees correspond nearly to the following numbers of Beau- 

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



1. the same as 1. Light breeze, 1 



2. " " " 4. Moderate breeze, 1 of Beaufort's 



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



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



[The force of the wind is now estimated and registered according to 

 the direction on the blank forms.] 



SKY. 



The blue color of the sky has an intimate connexion with the hy- 

 grometrical state and the electrical tension of the air ; it may be noted 

 by the ex})ressions, dat^k, light, and greyish. 



Haze and dry mist. — The transparency of the air is often disturbed 

 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 dif- 

 ferent names, appears frequently after long droughts ; in this country 

 it seems to characterize the Indian summer. In Europe, and else- 



