184 ON ROTATION OF CROPS. 



there intermixed with the oaks, will find a soil so well 

 adapted to them that they will germinate readily and grow 

 rapidly. Thus a wood of aspen and fruit-trees will suc- 

 ceed to one of oaks ; but, after a long course of years, the 

 old stumps and roots of oak, favored by the exudations of 

 the forest of a different family, will shoot out, and, in the 

 end, supplant the new forest, and a second forest of oaks 

 will be re-established, but not till after an assolement of 

 trees of another family. You see, therefore, that Nature 

 occasionally makes successive as well as simultaneous as- 

 solements. 



Caroline. This is very curious. I did not conceive it 

 possible for an assolement to take place where industry did 

 not interfere with the natural course of vegetation. But 

 this succession of crops must change once a century 

 rather than once a year. 



Mrs. B. They are doubtless of very long duration. 

 The assolements of trees which occur in the course of ag- 

 riculture are of a more transitory nature : they are gen- 

 erally made with a view to improve new soil, in order to 

 prepare it for cultivation, such as the simultaneous assole- 

 inent of broom and pines in the Campine of Belgium. 

 These shrubs enrich the soil for the future cultivation of 

 grain, both by their exudations and by the manure formed 

 from their leaves. 



I have seen a very singular assolement in the neighbor- 

 hood of the Rhine, consisting of alternations of vine and 

 clover. After a period of twelve years the vines are 

 grubbed up, and clover sown for three or four years. 



But the most remarkable assolement is that of water. 

 There are some districts in France in which the low 

 grounds are laid under water for the period of a twelve- 

 month, and this is renewed every seven years. 



Caroline. What harvest can be obtained from such a 

 culture, unless it be fish ? 



Mrs. B. Fish and wild fowl form, in fact, the only pro- 

 duce while the land is under water. This mode of culture 



1011 How is the establishment of a second forest of oaks de- 

 scribed 1 ? 101^. What is seen from this 1 ? 1013. What is 

 said of the duration of the assolement of trees'? 1014. With 

 what view are they made 1 ? 1015, What singular assolement 

 has Mrs. B. seen in the neighborhood of the Rhine"? 1016. 

 What more remarkable one s namedl 1017. What advantage 

 has it* 



