THE FARMER AT HOME. 19 3 



under water will be softened, if it be not held so as to meet the stream, 

 sparks being often produced even under water. 



GRINDSTONE. This is a circular stone used for the grinding 

 of edge tools, being mounted on a spindle, and turned by a winch- 

 handle or crank ; but in manufacturing establishments, where much 

 grinding is to be done, the stone is turned by water or steam. The 

 stone suited to form grindstones, is what is denominated a sharp grit, 

 that is, the grains of sand or siiex of which it is composed are pretty 

 uniform in size, and firmly attached to each other by a siliceous or 

 other very hard cement, without the interstices between the grains 

 being filled up, as frequently is the case, or nearly so, with the other 

 kinds of sandstone. A grindstone mounted on friction rollers can be 

 turned by a very small power applied, compared with what would be 

 required were it not on them ; and if there be a treadle attached to 

 the crank, in sharpening all small instruments the grinder can turn 

 it by his own foot, so as to save the time of a second person. 



GRINDSTONE. 



GUANO. This is a manure used in modern husbandry ; less in 

 this country than in England. It is merely the excrements of vari- 

 ous sea-fowls, which resort in immense numbers to small uninhabited 

 islands or rocky promontories on the coasts of Africa and South Amer- 

 ica, where they have remained in undisturbed possession for ages. 

 Some of the deposits there made by these birds are from fifty to sixty 

 feet in depth. Guano has been pronounced by competent judges to 

 be the richest manure known to the farmer ; but, as might be sup- 

 posed, it is of various qualities, depending not only on its original 

 character, but the climate and metereological influences upon it, 

 where obtained. Its original character was the result of the peculiar 

 food on which these birds feed, mostly flesh and fish, that afford a 



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