108 CHYMI3TRY APPLIED TO AGRICULTURE. 



Calcareous, sandy, and siliceous soils may be tilled at 

 any time, whilst the argillaceous soils are in a fit state for the 

 plough only at certain seasons, which must be eagerly 

 seized upon by the farmer ; the action of the plough upon 

 these lands immediately after rain, only leaves marks in 

 the mud ; and if they be allowed to remain till they are 

 thoroughly dry, they become impenetrable by it ; the in- 

 terval between these two periods is the time most favorable 

 for tilling. 



The best tilling does not always prepare soils entirely for 

 cultivation ; some are not sufficiently divided or crumbled ; 

 others are not sufficiently levelled, and it is only by the as- 

 sistance of the harrow, or the roller, that the labor of tillage 

 can be completed. By dragging the harrow in all direc- 

 tions over a newly ploughed field, the clods left by the 

 plough are turned over, the uprooted weeds are carried off, 

 and a more equal division is given to all parts of the soil. 

 The strength and weight of the harrow must be in propor- 

 tion to the resistance offered by the nature of the soil. The 

 harrow can be employed advantageously in opening the soil 

 of artificial meadows, especially those of clover, when the 

 surface has become a crust impenetrable by air or water ; 

 the operation of harrowing, in this case, should be performed 

 early in the spring of every other year, or immediately after 

 having cut the first crop of fodder; by this means, many 

 plants injurious to the soil are destroyed, and meadows are 

 restored, which would have been constantly deteriorating. 

 I have practised harrowing fields of grain, early in the 

 spring, with great success, and have found the harvests 

 from them uniformly much finer, than from those that had 

 not been harrowed ; but it was necessary to pay attention 

 to having the harrows very light, and made with wooden 

 teeth. 



The roller I have found to produce an excellent effect 

 after the seed was covered ; it unites and levels the surface 

 of the ground, and is particularly useful for porous and light 

 soils, and for those earths of which the constituent particles 

 are fine and light. If such soils have not received a suitable 

 degree of firmness from the roller, high winds and rains 

 are apt to carry off the upper layer, and to leave bare the 

 roots of the plants. Another advantage arising from the 

 application of the roller is, that the soil which has been 

 subjected to it, presents fewer obstacles to the use of the 

 scythe, or of the sickle. 



