APPENDIX 157 



and on the same principle as that of my orchard- 

 houses; nothing can be more perfect. In the figure 

 it will be seen I have left a small aperture under the 

 apex of the roof for the escape of rarefied air. In very- 

 hot weather this may be useful, but in my slate-floored 

 ground vineries I have not done this, and yet the 

 ventilation is perfect. I have not yet ascertained in 

 what manner the heated air escapes. The ventilating 

 apertures are all on the surface of the soil, and at the 

 same level ; but I suppose it stoops to get out, having- 

 no other mode of egress.. 



DIMENSIONS OF GEOUND VINERIES 



JSfo. 1, for a single vine in centre 



Width at base . . . . .30 inches. 



Slope of roof 20 inches. 



Depth in centre . . . .16 inches. 



iPb. 2, for two vines 14 inches apart 



Width at base 42 inches. 



Slope of roof . . . . .28 inches. 

 Depth in centre . . . .20 inches. 



These dimensions need not be arbitrary, for ground 

 vineries of larger dimensions may be made with every 

 chance of success, and Hamburgh grapes grown in 

 Bedfordshire instead of cucumbers; for no part of 

 England can be more favourable to grape culture 

 than the fertile, sandy districts of a portion of that 



