344 COMMON WEEDS 



Ponds and lakes have been cleared of slimy algae also 

 by placing copper sulphate in a sack and towing it up 

 and down in the water from the end of a boat. About 

 i Ib. of the chemical per 125,000 gallons of water in 

 the pond has been found suitable for the work. The 

 amount of water in the pond can be calculated with 

 sufficient accuracy by multiplying the average length, 

 breadth, and depth in feet together, and multiplying 

 this product by 6\ (the approximate number of gallons 

 in a cubic foot). 



4. The weeds of watercress beds must be dug out 

 or constantly pulled up by hand. 



" The seeds of most sorts of weeds are so hardy, as to lie sound and uncor- 

 rupt for many years, or perhaps ages, in the earth ; and are not killed until 

 they begin to grow or sprout, which very few of them do unless the land be 

 ploughed, and then enough of them will ripen amongst the sown crop to 

 propagate and continue their species, by shedding their offspring in the 

 ground (for it is observed they are generally ripe before the corn), and the 

 seeds of these do the same in the next sown crop ; and thus perpetuate their 

 savage, wicked brood, from generation to generation." 



J ET H R o T u LL , The Horse Hoeing Husbandry, 1731. 



