Meteorological Journal. 173 



West, 180^ is North, and 270°, East. The vane is moved by a 

 very faint breeze, and hence is seldom at rest. At each observa- 

 tion, its extreme excursions during an interval of about five min- 

 utes are noted, so that the observations in column seventh indi- 

 cate the variableness as well as mean direction of the wind. 

 This arc of vibration is commonly from thirty to forty degrees, 

 and sometimes even ninety and upwards. The mean of these 

 daily arcs I call the mean variableness, which will be observed 

 to be uniformly greater in the afternoon than forenoon. The 

 force of the wind is estimated by a scale in which indicates a 

 calm ,• 1 a breeze just perceptible ; 2 gently pleasant ; 3 brisk ; 

 4 very brisk ; 5 high wind. The mean direction of the wind 

 for the month is obtained, not by taking the mean of the num- 

 bers denoting the daily directions, which would be a very erro- 

 neous method, but in the usual mode of resolving a traverse ; the 

 wind's direction being considered the course, and its velocity the 

 distance. We wish to learn whether the atmosphere merely 

 oscillates to and fro, or has a progressive movement. The obser- 

 vations indicate the latter to be the case. The northerly and 

 southerly motions are nearly equal • but the westerly far exceeds 

 the easterly ; so that the absolute progress of the wind is nearly 

 from west to east, and at the mean rate of three or four miles 

 per hour. 



In column eleventh, indicates a sky perfectly clear ; 10 en- 

 tirely overcast. The clouds are always noted when they cover 

 one tenth of the visible heavens, and their direction when it can 

 be ascertained. Sometimes a stratum of clouds is so uniform and 

 unbroken, as renders it impossible to detect any movement. In 

 all cases it is the highest observed stratum which is recorded. 

 The mean direction of the clouds is deduced in the same way as 

 that of the wind, with the exception that all the clouds are ne- 

 cessarily regarded as moving with the same velocity. 



The rain gauge is a copper cylinder of ten inches diameter, ele- 

 vated 49 feet from the ground. The water is measured in a glass 

 tube of one inch diameter graduated to tenths of an inch. 



