The Infliicucc of Trees on RaiiifalL 



767 



keep the filter in jjusiiion. Tlio \vator is introduced to the tank 

 through a bed of gravel j^laeed outside the wall ; an arrangement 

 which prevents lilth from getting into the tank, and heing apart from 

 the interior can be renewed without disturbing the water. It must be 

 remembered that gravel is not a purifier, it only acts as a strainer ; 

 hence the utility of using it to receive the water from the conductor. 



If the fall is regular the water may be brought from the source to 

 the reservoir in flanged clay pipes with cemented joints, but when clay 



Sectional View of Eeservoir with Filter;^ . A is supply pipe ; B, gravel strainer ; 

 Cj filters ; D, draw-oft" pipe. 



pipes are used they ought never to be under 4 in. inside diameter. This 

 class of piping costs about five or six pence per foot. From the 

 reservoir to the house I would recommend cast-iron underground 

 faucet pipes coated with patent solution. Pipes of 2 in. inside diameter 

 will cost about one shilling and sixpence per yard. Bends, tees, and 

 traps to match, four shillings and sixpence per pipe of six feet lengths- 

 Reducing the foregoing statements into practice, I have constructed 

 ],100 yards of Avaterworks at the following outlay, viz., £]27 10s., all 

 complete as above. 



THE INFLUENCE OF TREES ON RAINFALL. 



From observations made by M. Fautrat, relative to the comparative in' 

 fluence of leafy woods and resinous on rain and the hygrometric state of 

 the air, recently communicated to the Paris Academy, it appears that 

 pine forests have a much greater influence on the hygrometric state than 

 others ; so that if the vapours dissolved in the air were apparent, like fogs 

 we should see forests shrouded in a large screen of moisture, and in the 

 case of resinous woods the vapoury envelope would be more distinct than 

 in that of leafy woods. M. Fautrat also shows that pines retain in their 

 l)rauches more than half of the water that is poured upon them, whereas 

 leafy trees allow 58 per cent, of the precipitated water to reach the surface 

 of the ground. He suggests, therefore, that in planting with a view to 

 oppose inundations, it would be advisable to choose l)y preference resinous 

 trees, as ottering a better coycvt.— Scicnce-Gos-'^ij), 



