158 Meteorological Observations for December 1827. 



Mean at 2 P.M. 78°-2— Mean at 8 A.M. 83°-0— Mean at 8 P.M. 85-5 



of three observations each day at 8, 2, and 8 o'clock . . . 82*2 



Evaporation for the month 0«60 inch. 



Rain near ground 5*625 inch.— Rain 23 feet high 5-115 inch. 



Prevailing Wind S.W. 



Summary of the Weather, 

 A clear sky, 3 ; fine, with various modifications of clouds, 9 ; an over- 

 cast sky without rain, 7h i foggy 2 ; rain, 9$.— Total 31 days. 



Clouds. 

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

 15 8 28 14 12 23 



Scale of the prevailing Winds. 

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

 li i 1 1 4 10£ 8 4| 31 



General Observations. — The weather to the 24th inclusive was remark- 

 ably mild for the season, but windy and wet, five inches and a quarter of 

 rain having fallen ; and on several days before the winter solstice it was 

 remarkably dark, from there being no opening in the prevailing strata of 

 clouds to admit the passage of the solar rays. 



Early in the morning of the 12th there was a thick fog, which gave out 

 a very strong sulphurous smell : the 29th was also distinguished by a cold 

 dense fog throughout the day and night. 



The last spring tides were high in Portsmouth harbour, and along the 

 southern coast, also at Liverpool, and along the western coast, in conse- 

 quence of so great a fall of rain, with accompanying south and south-west 

 gales. The highest spring tide was a few minutes before 12 p.m. on the 18th, 

 although it was the first after the change of the moon. The rain on the 

 18th, 19th, and 20th continued fifty hours without intermission. 



On the 21st and 22nd, thunder storms, with lightning and hail, were ex- 

 perienced in several places in Hampshire. 



On the 25th a parhelion appeared at mid-day on the western side of the 

 sun, when the cirrocumulus and attenuated cirrostratus clouds were beauti- 

 fully tinged with faint prismatic colours thirty degrees distant from the 

 sun's centre. 



The maximum temperature of the external air occurred in the nights of 

 the 3rd, 7th, 9th, 13th, 15th, 17th, 21st and 23rd, instead of in the days. 

 These frequent occurrences rendered the circumstance remarkable and de- 

 serving an explanation. It seems to be influenced by the sun's position in 

 the zodiac at this time of the year ; the temperature of the ground at and 

 near the surface; and the inosculation of the sea air with that over the 

 land in the evening, just before the coming on of rain from the western 

 side of our meridian. 1st. The sun's meridional altitude in this latitude in 

 December varies from 16 to 17| degrees, and from so great an obliquity 

 of his rays, or so small an angle, that from this altitude they make with 

 the horizon, only three or four degrees of thermometrical heat are pro- 

 duced near the earth's surface, more than the temperature of the ground. 

 2ndly. The temperature of the atmosphere in a wet December like the 

 present, depends very much on the temperature of the ground, and the 

 quality of the prevailing vapours, which, if humid and accompanied with 

 mild currents of air, then the temperatures of the ground and air are 

 found to coincide nearly. 3rdly. If under these circumstances of tempera- 

 ture and condensing state of the lower medium of the atmosphere, the 

 sea air should unite with the land air on the approach of rain after sunset, 

 on any day in December or January on which the temperature of the air 



has 



