XXX INTKODUCTION. 



Hampstead Heath, less than 100 acres in 1807, remains almost 

 untouched, except a few small inclosures. 



In the west of the county Enfield Chase was mostly inclosed 

 before 1787. In 1803, 1,500 acres were inclosed, as well as 2,746 acres 

 of common fields. The names of various lodges and gates are the 

 only local evidences of its former extent. South Minis inclosure 

 (1,000 acres) formed part of it. Edmonton Common (1,2-31 acres) 

 was inclosed before Enfield Chase. The waste places in the immediate 

 neighbourhood of London have been gradually absorbed by the 

 extension of buildings. Tothill Fields were beyond Westminster, 

 extending to the river ; Vincent Square occupies part of the ground, 

 which also included the site of Millbank Penitentiary. Wormwood 

 Scrubs (Wormholt Common, Wermer Wood Common) is still 

 open ground, south of Kensal Green, though 60 acres have been 

 enclosed ; it was formerly a wood of 200 acres. Old Oak Common is 

 a part of it, Eel-brook, or Hell-brook Common, a small piece of 

 ground between Little Chelsea and Walham Green, is gradually 

 becoming surrounded by buildings, and most of the less common 

 plants which it produced have disappeared through draining. Chelsea 

 Common occupied the ground between the King's Road and Bromp- 

 ton, on which Marlborough Road, etc. now stands. 



II.— CLIMATE. 



1. Tempeeature. — The mean or average temperature of a place is 

 the first thing to be determined in discussing its climate. This might 

 be done theoretically, by first determining the mean temperature of 

 each day for a considerable period, say three years, by observing the 

 temperature every alternate hour of the twenty-four, and then dividing 

 the sum by twelve. The mean temperature of each month is 

 obtained by dividing the sum of the mean daily temperatures by the 

 number of days it contains ; and of the year, by dividing the sum of 

 the mean monthly temperatures by twelve. Monthly means can, how- 

 ever, be determined from a single daily observation, as the monthly 

 mean of observations taken at a particular hour differs irom the 

 monthly mean temperature by a quantity which is constant for each 

 particular month, and can be applied as a correction. It was formerly 

 usual to determine the mean temperature of a mouth by taking the 

 mean of the maxima and minima, but this gives a result which is 

 to-) great for every month except December. The mean annual tem- 

 perature at the sea level becomes less by 0-9°, or about one degree for 



