THE RELATION OF METEOROLOGY TO HORTICULTURE. 17 



0 inches, whilst the average yearly fall is rather more than 137 inches. 

 However, a week without rain is not unknown even at Seathwaite. This 

 place affords an excellent illustration of the way in which rainfall is 

 produced through the cooling of air by its expansion. The moist air, 

 which reaches the southern part of Westmoreland from off the sea, 

 sweeps upwards towards the hills, and in the neighbourhood of the 

 Styehead Pass is driven through a deep valley up the pass to a con- 

 siderable height, and this results in the copious condensation and fall of 

 rain at Seathwaite, which is just beyond. Last year the largest fall 

 recorded in Great Britain was above 205J inches at Gleslyn, on 

 Snowdon, whilst the least was but little more than 19 inches at Boy ton 

 in Suffolk. 



A still more striking instance of this kind is to be found in India at 

 Cherrapungee, on the slope of the Khasia Hills, where the average annual fall 

 of rain amounts to 500 inches, and occasionally exceeds 600 inches, the air 

 in that case being the vapour-laden south-west monsoon from off the Bay 

 of Bengal. We sometimes are inclined to think that our rainfall is exces- 

 sive, but compared with that of Cherrapungee even a Snowdon fall of 205 

 inches becomes very insignificant indeed. 



As an example of a less favoured region I might mention Egypt, where 

 the rainfall does not exceed a couple of inches in a year, but where, under 

 the strong sun and parched air, the evaporation exceeds 100 inches in the 

 year. What this amount of evaporation means may be inferred from the 

 fact that, in connexion with the Nile Dam, in summer about 400,000 tons 

 of water has to be held up daily to balance the loss by evaporation. 



In the driest parts of our own country the rainfall in summer is about 

 balanced by the evaporation, and therefore the water required to supply 

 springs and underground water has to be drawn from the winter falls ; 

 but in the wettest districts the rain which falls is, all the year round, 

 far in excess of the amount evaporated. It may happen, however, that 

 although the surface soil may be well saturated the reserves in the earth 

 may at the same time be very limited, and this condition might very well 

 lead to stagnation in plant growth in the drier seasons of the year. 



The conservation of rain water is a matter of practical importance to 

 horticulturists, who grow plants under glass covering a large area, espe- 

 cially in the neighbourhood of towns. These glass roofs collect large 

 quantities of water, which might be stored in tanks underground and 

 pumped by wind power to supply the houses as required. Where water 

 has to be purchased from the water companies the saving in cost which 

 would result from such a plan carefully thought out should suffice to pay 

 interest and to form a sinking fund on the capital expenditure needed to 

 carry it out. 



The amount of the rainfall has an important influence upon the 

 character of the plant life of a district or of a country. A few slides will 

 indicate this clearly and briefly. The first shows a ravine in the side of 

 a hill-slope above Loch Fyne, eroded by the action of the water draining 

 the hills and running down to the loch. The course of the ravine is 

 plainly seen by the vegetation which covers its sides, whilst the debris 

 which has been carried down by the stream has formed a fertile delta 

 extending some distance into the loch itself. Other slides will give US an 



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