60 ROYAL WATER-LILY. 



was added a ledge all round, nine inches deep, three 

 and a half wide, and heated by a triple row of small 

 lead pipes, through which hot water circulated. By 

 these means, the tank was rendered nineteen feet 

 square, with a deep centre and shallow sides. In 

 order to keep the water in motion, a small wheel 

 was added at one corner ; over that wheel water was 

 caused to drop continually with force enough to keep 

 the wheel constantly revolving; the water thus con- 

 tinually flowing into the tank is carried off by a 

 small pipe in one of its corners near the bottom. In 

 this way were secured the important advantages of 

 the water being so often changed that it could not 

 become stagnant, together with ceaseless gentle agi- 

 tation. Nothing could be more like the natural state 

 of a tranquil river. By the heating apparatus, its 

 temperature could also be regulated with facility. 

 The thermometer has generally indicated 85 degrees. 

 In the centre of the tank was introduced a hillock 

 of earth, consisting of burnt loam and peat. To the 

 burning of the loam Mr Paxton attaches great im- 

 portance; and this agrees with the daily experience 

 of those who employ burnt or charred materials in 

 gardening. The physical condition of the soil is 

 much improved by the process, and the weeds and 

 insects are destroyed. Mr Paxton is also of opinion 

 that the removal by fire of all matters ready to en- 

 ter into fermentation or rapid decomposition when 

 in contact with water heated to 85 degrees, was in 



