TAKEN AT HOLLY BANK, "WATFOED, 1876-77. 



223 



menced on the 21st, being the entire cause of the slight reduction 

 of 3° in the mean temperature of the whole month. The minimum 

 Tras below 32° on the 25th only. Pressure was almost invariably 

 below 30 inches until the 20th — the warm period. During the 

 succeeding cold period it was above 30 ins. without a single 

 exception. The rainfall was almost entirely confined to the first 

 16 days, for 12 of which the wind was S. or S.W. The prevailing 

 direction during the diy period which followed was N.E. A re- 

 markable phenomenon was observed on the 6th. At about 10 '45 

 a.m. a dense black cloud suddenly formed and it became as dark as 

 in the worst London fogs. In a few minutes rain began to fall 

 and it was quite light. At about 11 a.m. the rain ceased, the 

 cloud again formed, and it became nearly as dark as before, when 

 rain again fell and dispersed the cloud. The difference between 

 the dry- and the wet-bulb thermometer at the time was less than 

 half a degree, showing an excessive moisture of the air. There was 

 a thunderstorm at 8 p.m. on the 5th. On several mornings there 

 was a dense mist on the ground, clearing off before 9 a.m. 



November. — Atmospheric pressure was high, above 30 inches, 

 at the beginning of the month, decreasing to 29-171 ins. at 9 p.m. 

 on the 12th, increasing again to the 22nd (30*294 at 9 a.m.), and 

 then again decreasing. The cold weather which commenced on 

 the 21st of October continued throughout the month, the only 

 warm period being from the 14th to the 19th. The mean of these 

 six days was 50°-3, being 8° above the mean of the entire month. 

 The minimum was below 32° on six days, all between the 1st and 

 13th, and on the 11th was lower than on any other day in the 

 three winter months — December, 1876, and January and February, 

 1877. The wind was mostly northerly to the 10th, variable 

 (easterly prevailing) from the 11th to the 26th, and S.W. the last 

 four days. The rainfall was pretty equally distributed over the 

 month. There was a slight fall of snow on the 8th. 



December. — A remarkable depression of the barometer occurred 

 on the 4th, exceeding that of the 12th of March, but it was 

 not (at Watford) accompanied like it by any great atmospheric 

 disturbance. Pressure was generally slight, but very variable, as 

 the following daily readings of the barometer at 9 a.m. will show. 

 The mean will be found to be 29-490 ins., differing very slightly 

 from the mean of the 9 a.m and 9 p.m. readings togethei-, as given 

 in the table (opposite j). 218). 



ms. 



29-439 

 •280 

 -093 



28-395 

 -927 



29-041 

 •179 

 •526 



ins. 



30-126 

 •204 

 •142 



29-743 

 •731 

 •934 

 •936 

 •820 



It will be seen that there are two principal minima, first that of 

 the 4th, and secondly that of the 20th, on which day at 9 p.m. the 



