426 Hemarlcs, and Ohservations suggested 



of the rain, and the heats and colds of the atmosphere, have a 

 tendency to reduce the inequalities in the soil, and bind it into 

 a solid mass, which is cold and unproductive when compared 

 with soil which has been properly pulverised. If intended for 

 deep-rooted crops, the soil should be broken up to a consider- 

 able depth in dry weather, in order that the particles into which 

 the soil is divided, being thoroughly dried, may preserve its 

 open texture as long as possible; confined air is thus gene- 

 rated between the particlesof soil, which is the best retainer of 

 heat, as we have all every day experience from the comfortable 

 warmth afforded by our clothes. This confined air retains the heat 

 imparted by the sun through the day, which accumulates and 

 becomes very sensible in all free open soils ; and keeps up a higher 

 temperature in the night, thus showing the necessity of bottom 

 heat to all plants wherever grown, it being natural to all good 

 well-pulverised soils. The free admission of atmospheric air is 

 also necessary in the decomposition of the food of plants ; by 

 parting with its oxygen, it helps to fix and retain the carbon in 

 the state of carbonic acid, and in the act of separation always 

 gives out heat ; and it is also the great source of nitrogen, which 

 chemists have of late more frequently discovered in plants, and 

 which, Dr. Lindley says, is indispensable to the healthy condition 

 of the young spongioles of the roots. To keep the soil open, it must 

 be well drained where necessary, and must be stirred in spring 

 when in a dry state : if broken dry into small pieces, and well 

 dried before heavy rains occur, it keeps open till again flooded 

 with the heavy rains of next winter ; the small interstices between 

 the particles are filled with confined air, which retain heat, and 

 moisture is retained by the capillary attraction which water has 

 to the sides of narrow apertures ; hence the smaller these par- 

 ticles can be made, if worked dry and kept asunder, the more 

 heat and moisture is retained near the surface. When soil has 

 been some time exposed to the air by digging and turning up in 

 the spring, if the weather is dry and frosty, the freezing of the 

 water contained in the soil causes it to expand; and, if the ground 

 is strong and clayey, it is beneficial in reducing coarse and lumpy 

 soils to a finer texture on the surface : if done in summer, in 

 dry weather, the heat, if considerable, expands the water, and the 

 same reduction of texture takes place, though more slowly, as 

 the expansive power of freezing is generally greater ; by degrees, 

 however, the particles, by attrition and the action of the atmo- 

 sphere, are reduced into small powder, which is washed down 

 by the heavy rains of winter ; and the pressure of the soil above 

 consolidates the earth into the same solid mass as we had the 

 year before, requiring to be again opened up in the spring. 

 When ground has thus been operated upon for a succession of 

 years, it will not keep open so well, has a constant tendency to 



