26 WIND- V AXE. 



sixteen points of the compass, viz: N. NNE. NE. EXE. E. 

 ESE. SE. SSE. S. SSW SW. WSW. W. WNW. NW. 

 NNW. 



The lower, or surface wind, often has a different direction from 

 that which prevails in the upper regions of the atmosphere, and 

 this is generally the case when the wind turns, and the weather 

 is going to change, also during storms and great atmospheric 

 movements. The direction, then, of the lower and the higher 

 layers of clouds must be separately noted in the several columns 

 of the journal reserved for this purpose. If the direction is the 

 same in the whole extent of the atmosphere, the same letters will 

 be marked in the three columns. If the absence of clouds does 

 not permit us to judge how the wind is above, a dash must be 

 substituted for the letter, indicating that the observation has been 

 made. A blank always signifies an observation omitted. 



To avoid an error in the estimate of the direction of the clouds, 

 it will be well to observe their course between two fixed points, 

 as a window frame, the fixed lines of which will facilitate the 

 observation. Another very convenient method is to place a small 

 mirror horizontally, with lines traced on it indicating the points 

 of the compass ; the image of the clouds passing over these will 

 indicate their direction. 



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

 in which the winds succeed each other in the course of the day, 

 must be watched very carefully. It will be seen that they com- 

 monly 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 back in the opposite direction, 

 particularly during storms. A little memorandum, summing up 

 in a few words at the end of each day this course of the wind, 

 together with the hours 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 

 according to the following degrees : : 



0. A perfect calm. 



The simple initial letter of the wind, for instance N. (north), 

 indicating its direction without any number, means a slight move- 

 ment of the air hardly to be called a wind, and only just sufficient 

 to allow an estimate of its direction. 



