"78 Meteorological Observations for May 1831. 



METEOROLOGICAL OBSERVATIONS FOR MAY 1831. 



Gospoii: — Numerical Results Jbr the Month. 



Barom. Max. 30-303. May 9. Wind N.E.—Min. 29-478. Mayl. WindS. 

 Range of the mercury 0-825. 



Mean barometrical pressure for the month 29-920 



Spaces described by the rising and falling of the mercury 4-096 



Greatest variation in 24 hours 0-286. — Number of changes 22. 

 Therm. Max. 72°. May 25. Wind S.E.— Min. 35°. May 6. Wind N. 

 Range 37°. — Mean temp, of exter. air 54°'76. For 31 days with © in 52-85 

 Max. var. in 24 hours 20°00.— Mean temp, of spring-water at 8 A.M. 49-60 



De Luc's Whalebone Hygrometer. 

 Greatest humidity of the atmosphere, in the evening of the 29th.... 94° 

 Greatest dryness of the atmosphere, in the afternoon of the 18th... 43 



Range of the index 51 



Mean at 2 P.M. 57°-5.— Mean at 8 A.M. 62°-7.— Mean at 8 P.M. 68-5 



of three observations each day at 8, 2, and 8 o'clock 62-9 



Evaporation for the month 6-35 inches. 



Rain in the pluviameter near the ground 2-07 inches. 



Prevaihng winds, S.E. and N.E. 



Summary of the Weather. 

 A clear sky, 5^ ; fine, with various modifications of clouds, 1 5i ; an over- 

 cast sky without rain, 4^ ; rain, 5;*. — Total 31 days. 

 Clouds. 

 Cirrus. Cirrocumulus. Cirrostratus. Stratus. Cumulus. Cumulostr. Nimbus. 



25 10 25 22 15 13 



Scale of the prevailing Winds. 



N. N.E. E. S.E, S. S.W. W. N.W. Days. 



3i 8 4 8i 4 4i 1 1 31 



General Observations. — This month has been alternately wet and dry ; 

 the dry period was from the 5th to the 19th, during which time no rain 

 fell here, and the air was frequently ai'id with a North-east wind, accom- 

 panied with a great evaporation. 



For several days upwards of three-tenths of an inch evaporated, and on 

 the 18th, the day before the rain came on, half an inch in depth ascended 

 from the evaporator, which clearly indicates the greater power of the air 

 in eliciting heat, and carrying oft' so much moisture from near the surface 

 of the earth immediately before the change from dryness to rain, and 

 which was verified by the hygrometer's, then pointing out the maximum 

 dryness for the month. 



There were several hoar frosts in the first part of the month, when great 

 blights prevailed, and their effects have since been made manifest by the 

 trees being much thinned of their fruit. Comparatively speaking there 

 were but a few warm days this month, and the mean temperature of the 

 external air is about one degree under the mean of May for many years past. 



On the 5th, at three P.M. a heavy flash of lightning was experienced 

 here, and was succeeded by a loud clap of thunder; distant thunder also 

 frequently occurred in the morning of the 24th. 



At half-past ten o'clock in the night of the 30th, a few light corusca- 

 tions ascended due North from an aurora borcalis, which was low in the 

 Northern horizon, and two meteors fell over it. This may be considered 

 late in the sprir)g for its appearance, as the evening twilight in that quarter 

 is getting long, and being of a similar appearance to that of an aurora, it 

 renders it imperceptible in the summer months. 



The 



