104 JOURNAL OF THE ROYAL HORTICULTUR.AL SOCIETY. 



METEOROLOGY IX ITS RELATION TO HORTICULTURE. 

 By R. H. Curtis, F.R.Met.Soc. 



[Lecture given on August 28, 1906.' 



It will be unnecessary for me to do more than remind horticultm-ists 

 that a very intimate connection exists between the phenomena exhibited 

 in the growth of plants and several climatological elements whose varia- 

 tions it is the business of meteorologists to observe and record. 



The existence of such a connection was very early recognised by the 

 Royal Horticultural Society, and so far back as the year 1825 it gave 

 expression to its sense of the importance of studying the relations between 

 the two sciences by organising a series of climatological observations at 

 Chisw^ick, which was continued uninterruptedly for fifty years. A break 

 then occurred, but after a short interruption the observations were 

 resumed with an improved equipment of instruments, the station having 

 been reorganised by Mr. Edward Mawley, V.^I.H., whose name is so well 

 known in connection with phenological and meteorological matters, as 

 well as in the horticultural world. 



This second series had necessarily to cease when the Society removed 

 its operations from Chiswick to Wisley ; but at Wisley an excellent site 

 has been allotted to the Meteorological Station, its instrumental equip- 

 ment has been extended, and daily observations have been regularly made 

 since the beginning of 1904. 



It is satisfactory to know that these Chiswick observations have been 

 frequently made use of by botanical physicists both in this country and 

 on the Continent ; and the Society may also congratulate itself upon the 

 fact that it was probably the first public body in this country to organise 

 and carry out such systematic climatological observations. 



The meteorological elements which are of most direct interest to the 

 horticulturist are : — 



Solar radiation. 



Temperature of the air and soil. 

 Humidity of the air. 



Amount of moisture precipitated as rain, dew, mist, &c. Direction 

 and force of wind. 



I do not propose to attempt the impossible task of dealing with each of 

 these elements in a single lecture, but to confine my remarks to the subject 

 of temperature, which necessarily involves a reference to solar radiation. 



First of all, let me try to make clear what it is the meteorologist 

 observes and records. 



In taking the temperature of the air, his object is to get the actual 

 temperature of a stratum of free air at a definite height above the ground. 

 To secure this it is essential that his thermometers shall be freely exposed 

 to the air current, but that at the same time they shall be protected from 

 the direct eft'ect of both solar and terrestrial radiation. 



