94 J. HOPKINSON METEOEOLOGICAL OBSERVATIONS 



mercury was at its lowest point, 29-101 ins. at 9 p.m. on the 4th, 

 after which it was unsteady for the greater part of the month, 

 rising to 30-257 ins., its highest point, at 9 a.m. on the 20th, and 

 to the same again at 9 p.m. on the 30th. At about 4.30 p.m. on 

 the 4th, the day of lowest pressure, there was a remarkable and very 

 destructive storm in the neighbourhood of Ware, which has been 

 fully described by Lieut. Croft, r.L.S., in our 'Transactions.'* 

 At Watford it was scarcely felt, there being only a slight thunder- 

 storm in the evening, with heavy rain commencing at about 1 1 p.m., 

 accompanied by a strong S.W. wind. At Enfield, between 4 and 

 4.20 p.m., hailstones three-quarters of an inch in diameter are re- 

 corded to have fallen, and considerable damage was done.f The 

 temperature of the air was much more uniform than in March ; but 

 the last half of the month was much colder than the first half, the 

 mean temperature from the 1st to the 15th being 46°- 6, and from 

 the 16th to the 30th, 42°-6. The maximum of the 4th (BO'^-l) was 

 only reached within 5° on one other day, the 22nd, when 58°-8 

 was recorded. The wind was mostly easterly, inclining to SE. the 

 first half of the month — the warm period — and to the jS'.E. the last 

 half — the cold period. Most of the rain fell during the warm 

 period, and there was none after the 23rd, when the first really 

 fine weather of the year commenced, there not having been more 

 than three days in succession without rain up to this time — not 

 only in the year, but from the beginning of November. Although 

 more rain fell than in the previous month, the air was considerably 

 drier, the degree of humidity being 12 per cent, less, as shown in 

 the table. Hail fell on the 4th, 5th, and 17th. The morning of 

 the 9th was foggy. 



May. — The first few days were remarkably cold, and during the 

 six days from the 3rd to the 8th the minimum was below 32"^ on 

 five. The following readings of the minimum thermometer give a 

 mean low night temperature, for this period, of 29°-4, which is 

 14°'2 lower than the mean minimum readings of the next seven 

 days, and 10° -6 lower than the mean minimum of the month. 



Atmospheric pressure was high at the beginning of the month, 

 being 30-418 ins. at 9 p.m. on the 1st, after which it gradually 

 decreased to 29-401 ins. at 9 p.m. on the 10th, increased in an 

 almost equally gradual manner to 30-256 ins. at 9 p.m. on the 

 22nd, and again decreased to 29-249 ins. at 9 a.m. on the 28th. 

 The prevailing direction of the wind was north-easterly for the 

 first half of the month, S. to S.W. on the 16th and 17th, then 

 northerly to the 25th, S.E. on the 26th, and south-westerly for the 

 last five days. No rain fell until the 9th, there being thus, from 

 the 23rd of the previous month, fifteen days without rain ; but 



* Vol. I, p. 230. 

 t Symons' ' Meteorological Magazine,' vol. xii, p. 43. 



