32 GARDEN MANAGEMENT. 



tion, as it is now rlelivered to the inhabitants of London, contains a pound of 

 chalk held in solution by this proportion of carbonic acid for every 560 gcillons. 

 Now it is found that, on mixing forty gallons of lime-water, or water in which 

 nine oimces of quicklime is dissolved, with 560 gallons in which a pound of 

 chalk is held in solution by seven ounces of carbonic acid, a haziness fu'st 

 occurs in the water, then it deepens into a white liquid, and soon assumes the 

 appearance of a well-mixed whitewash. When the agitation subsides, it is 

 found that the nine ounces of quicklime has again absorbed the seven ounces 

 of carbonic acid, and that both that and the pound of chalk have been preci- 

 pitated, learning the water over it perfectly pure. Availing himself of these 

 apparently opposing properties of chalk. Dr. Clarke proposes, when water is 

 impregnated with lime or chalk, to have two cisterns, one in which lime-water 

 is prepared, and another fourteen times larger, in which chalk is held in solu- 

 tion by the addition of the above proportion of carbonic acid ; with a third 

 cistern, in which the pure water can be drawn oflf. Dr. Clarke has proposed to 

 do this for the water supply of all London, and the cost, he estimates, would 

 not exceed £10 each day, an expense which would be much more than balanced 

 by the value of the chalk precipitated, which would amount to many hundred 

 tons per annum. 



87. Lime and chalk being the chief agents in rendering water hard and un- 

 suitable for domestic purposes, this mode of purification presents itself at once 

 efl&cient and practicable. Whei'e the more subtle salts are present in sufficient 

 force to impart an offensive flavour, good water must be sought elsewhere. 



88. Elevatio'ii. — A healthy site should also be elevated above the sur- 

 rounding country. How beautifully the immortal INIilton expresses this idea 

 in the words already quoted. For many reasons, the south aspect and the side 

 of a hill is the best of all positions. It will either be naturally dry, or capable 

 of being easily rendered so by efficient drainage. It will be warm, by absorbing 

 the greater part of the sun's rays, and being sheltered by the rising hill behind 

 it. It may generally be economically watered by diverting the course of some 

 trickling stream fi)r the purpose ; or, if a well is dug at the highest part of the 

 ground, the water may be easily and cheaply conveyed wherever it is wanted. 

 Such positions also enjoy immunity from those heavy fogs, and blinding mists, 

 so characteristic of many of our most beautiful valleys. Where these mists 

 abound, some of the loveliest houses, and most beautiful gardens, are enveloped 

 in a thick covering of wateiy vapour during the most enjoyable hours of the 

 TOoraing and evening. Nothing can well be more antagbnistic to health, or 

 opposed to true enjoyment, than a garden so enwrapped in early morn and 

 dewy eve. The dreamy hour of twilight cannot be enjoyed In the garden, 

 except at the rtsk of sore throats, catarrh, and lung disease. The more charm- 

 ing the scene, the greater the deprivation,— ^ the greater the danger to health. 

 To be driven out of the garden by a sudden invasion of fog ; to be compelled to 

 shut the drawing-room windows amid the depai-ting gloi-ies of the setting sun, 

 is by no means pleasant. An elevated position is also free from the noxious 

 effluvia so prevalent in low marshy localities, which will sail up the bottom of 



