OF WATERING PLANTS. 143 



gin of this dread ful''-malady was for a long time an inexpli- 

 cable mystery ; and it is only lately that Dr. Sette having 

 observed that it was confined to those districts in which 

 the maize, instead of being preserved in the ear, was kept, 

 like wheat, in separate grains, ready to be ground into 

 flour. This led him to suspect that the grain might have 

 acquired some deleterious property ; and, on examining it 

 with a microscope, he discovered that that part of the 

 grain, by which it had been attached to the husk, was cov- 

 ered by a species of mould of a poisonous nature ; there is, 

 therefore, every reason to believe that this fatal disease 

 arises from feeding on maize in this corrupt state ; and if 

 so, the disease might be easily guarded against. 



Emily. What a fortunate discovery ! The remedy is 

 so simple, it is merely to adopt the usual mode of pre- 

 serving maize in France and Switzerland, by hanging it 

 up to dry in the ear. 



Mrs. B. Certainly. We have hitherto considered only 

 the various modes of administering water ; but it some- 

 times happens that the earth is too moist : it is necessa- 

 ry, therefore, for the purposes of agriculture, to be ac- 

 quainted with the best mode of draining it. This opera- 

 tion may be performed in several ways-. When the local- 

 ity will admit of constructing a reservoir in a lower situa- 

 tion to receive it, the water may be carried off by subter- 

 raneous ducts. These conduits should be filled with 

 pebbles, sufficiently large to leave a free passage for the 

 waters between them. 



Caroline. But of what use are the stones ? why not 

 leave the channel quite free and open ? 



Mrs. B. The stones may be considered as forming a 

 sort of loose wall which serves to support the duct, by 

 preventing the top and sides from falling in : the water 

 would soon wear them away, were they not thus defend- 

 ed, and the passage be obstructed. 



The operation of draining a marsh is of much greater 

 importance. A marsh is a space of ground on which the 

 water remains too long, either for want of means of run- 

 ning off laterally, or because a layer of clay soil prevents 

 it from filtering downwards. 



795. How did Dr. Sette account for it? 796. When the earth is 

 too moist, what is to be donel 797. How may this be done! 798, 

 What is a marsh 1 



