8z THE ART AND PRACTICE OF LANDSCAPE GARDENING. 



bottom as possible, and pass out as near the top as may be. In 

 vineries the roots of the vines may be allowed to grow on the 

 inside or the outside of the houses. As a rule, the front walls of 

 vineries and peach-houses are built on arches, so that the roots 

 may spread in every direction. The greatest care must be taken in 

 the formation of a vine border. It is well to lay a pavement, 

 about 4 ft. beneath the surface, of rough material, and from this 

 take pipes, so that the stratum may be perfectly drained ; then, on 

 this foundation to fill in a mixture composed of best top spit loam, 

 of "/ m - bones, and of soot. The paths inside vineries and peach- 

 houses are best made of perforated iron. In stoves and growing- 

 houses make the footways of concrete floated with cement, or of tiles 

 laid in cement. On falling ground, ranges of hothouses should be 

 built vertically, and stepped when required ; though the path inside 

 should be made on the slope, and steps between the houses avoided. 



The temperature of hothouses is best attained by employing a 

 low-pressure hot water apparatus. Its operation is based on the 

 fact that water is at its greatest density and minimum volume at 

 39-2 Fahrenheit. When the temperature is raised above this point, 

 the volume of water increases and the density decreases ; so that 

 if we allow a given quantity of hot or cold water to intermingle, 

 the result of difference in the respective specific gravities will be 

 that the superheated water will expand and rise, propelling the 

 colder water, that, having given off its heat, returns to the boiler. 

 And so two columns of water are employed ; one is maintained 

 hotter than the other, whilst communication is kept between them, 

 and circulation by displacement is continually going forward. In a 

 boiler there are two openings, the one at the top and the other at 

 the bottom. From the upper opening a pipe is taken, which returns 

 after a certain distance to the opening in the bottom of the boiler. 

 From this point another pipe is led, communicating with a water 



