§ 149. It is recommended that in general public cemeteries should be placed at the east or the north, or the north-east of a town: the south and south-west winds, being usually moist, hold the putrefactive gases in solution more readily than the north, or north-east winds, which are dry. The higher the elevation of a cemetery, the nearer may it be permitted to a city, as putrefactive gases are lighter than the atmosphere and ascend. For the same reason, cemeteries lower than the houses should be at a greater distance. A site, with a slope to the south, is deemed the best, as it will be drier and warmer, and facilitate decomposition. § 150. Competent witnesses declare, that by a careful preparation of the ground, and without any appliances that would be otherwise than acceptable to the most fastidious minds, the escape of miasma may be so regulated as to avoid all injury to the health, and springs may be protected from pollution by drainage; and that by these means the necessity of far distant sites, and the inconvenience and expense of conveyance of the remains, and obstructions to the access of friends to the place of burial, may be avoided. § 151. Amongst these means, one for preventing the escape of emanations at the surface by absorbing and purifying them, is entirely in accordance with the popular feeling. The great body of English poetry, which it has been remarked is more rich on the subject of sepulture than the poetry of any other nation, abounds with reference to the practice of ornamenting graves with flowers, shrubs, and trees. A rich vegetation exercises a powerful purifying influence, and where the emanations are moderate, as from single graves, would go far to prevent the escape of any deleterious miasma. It is conceived that the escapes of large quantities of deleterious gasses by the fissuring of the ground would often be in a very great degree prevented by turfing over the surface, or by soiling, that is, by laying vegetable mould of five or six inches in thickness and sowing it carefully with grasses whose roots spread and mesh together. At the Abney Park Cemetery, where the most successful attention is paid to the vegetation, this is done; but in some districts of towns it marks the impurity of the common atmosphere that even grass will not thrive; and that flowers and shrubs which live on the river side, or in spaces open to the breeze, become weakly and die rapidly in the enclosed spaces in the crowded districts. Several species of evergreens, and the plants which have gummy or resinous leaves, that are apt to retain soot or dust, die quickly. The influence, therefore, of a full variety of flowers and a rich vegetation, so necessary for the actual purification of the atmosphere, as well as to remove associations of impurity, and refresh the eye and soothe the mind, can only be obtained at a distance from most towns. It occasionally happens that individuals incur expense to decorate graves in the town churchyards