238 TENTH ANNUAL REPORT OP 



The liigliest point wliicli it reaches during, or immediately after 

 the storm. 



If alternations of rising and falling take place, the fact should he 

 mentioned and the time noted. 



The thermometer. — The fluctuations of the thermometer in the 

 same time as those of the barometer should also he noted, and their 

 connection with the changes of the wind be obKserved. 



The wind. — It is of the greatest importance to observe the course 

 of the winds through the entire height of the atmosphere during the 

 whole continuance of the storm, by means of the wind-vane and of 

 the clouds in the different layers of the atmosphere. 



The hour when the wind begins, and the direction whence it comes; 



The moment of its greatest violence; 



The instant it changes its direction, and when it takes the direction 

 it keeps to the end of the storm. 



It should be stated if the wind blows in a continuous manner or in 

 squalls, and what is its force. 



If there should be one or more moments of calm, the hour and du- 

 ration will be indicated. 



Great care must be taken at each observation to note also the direc- 

 tion of the different layers of clouds, which will very often be found 

 different from that of the wind below, for the whole duration of the 

 storm. 



The clouds. — Are there certain forms of clouds which announce the 

 approach of a storm ? It is necessary, in this connection, to watch 

 the formation of the cirrus, the cirro-cumulus, cirro-stratus, their ar- 

 rangement in parallel lines, their course, and their directions. Note 

 the quarter of the sky first covered with clouds ; the moment when it 

 is entirely covered ; if there are later clear spots or not ; the moment 

 when the sky clears off. 



The rain. — Note the hour at which the rain or the snow begins 

 and ends ; measure the quantity fallen while the storm lasts. 



ACCIDENTAL METEORIC PHENOMENA. 



These v/ill be entered in the tables, in the place reserved for this 

 purpose on the opposite side of the sheet. If the space is not suf- 

 ficient for the description to be given, the phenomenon should be 

 simply noted, and reference made to a separate account for details. 

 Thus: 



Ihe solar and lunar haloes — that is, the colored circles sometimes 

 observed round the sun and moon. Distinguish the small ones, the 

 ring of which measures only a few degrees, from tlie large or real 

 haloes, the ritog of which has a diameter of about forty-four degrees. 

 It must be stated whether they are connected with other circles, as is 

 sometimes the case. Care must be taken not to mistake a part of a 

 grand halo for a rainbow. Note whether these appearances are, or 

 are not, ordinarily followed by rain. 



The Parhelia and Paraselenes, {mock-suns and moons.) — Describe 

 exactly their forms and the state of the heavens at the moment of 

 their appearance. 



