THE FARMER AT HOME 137 



DUCTILITY. In physics, a property possessed by certain solid 

 1 odies, which consists in their yielding to percussion or pressure, and 

 i i receiving different forms without breaking. Some bodies are duc- 

 1 le both when they are cold, and when they are hot, and in all cir- 

 ( umstances. Such are metals, particularly gold and silver. Other 

 1 Bodies are ductile only when heated to a sufficient degree ; such as 

 M'ax and other substances of that kind, and glass. Other bodies, 

 ; >articularly some kinds of iron, called by the workmen red-short, brass, 

 ;ind some other metallic mixture, are ductile only when cold, and 

 Brittle when hot. The degrees of heat requisite to produce ductility 

 n bodies of the first kind, vary according to their different natures, 

 tn general, the heat of the body must be such as is sufficient to reduce 

 to a middle state betwixt solidity and perfect fusion. As wax for 

 instance, is fusible with a very small heat, it may be rendered ductile 

 by a still smaller one ; and glass, which requires a most violent heat 

 for its perfect fusion, cannot acquire its greatest ductility until it is 

 made perfectly redhot, and almost ready to fuse. Lastly, some bodies 

 are made ductile by the absorption of a fluid. Such are certain 

 earths, particularly clay. When these earths have absorbed a suffi- 

 cient quantity of water, to bring them into a middle state betwixt 

 solidity and fluidity, that is to the consistence of a considerably firm 

 paste, they have then acquired their greatest ductility. Water has 

 precisely the same effect upon them in this respect, that fire has upon 

 the bodies above-mentioned. 



DURATION OF PLANTS. The several kinds of plants vary 

 very much in their degrees of longevity, some being annual, perfecting 

 their growth within a year, ripening their seeds and perishing. Others 

 are perennial and continue to grow and flourish for years and cen- 

 turies. Warm or cold climates have much influence on the duration 

 of plants, and in some few instances plants that are annual in cold 

 climates, become perennial when transplanted into warm regions, and 

 vice versa. There are some kinds of trees that are very short-lived, 

 as the peach and the plum, others reach a great age as the pear and 

 the apple. Some kinds of the forest trees are remarkable for their 

 duration, and specimens are in existence seemingly co-eval with the 

 date of the present order of things on our globe. The oak and chest- 

 nut or pine of our forests reach the age of from three hundred to five 

 hundred years. The cypress or white cedar of our swamps has fur- 

 nished individuals eight or nine hundred years old. Trees are now 

 living in England and Constantinople more than one thousand years 

 old, of the yew, plane and cypress tree varieties ; and Addison found 

 trees of the boabab growing near the Senegal in Africa, which, reckon- 

 ing from the ascertained age of others of the same species, must have 

 been nearly four thousand years of age. It may be remarked that 

 plants of the same variety attain about the samo age in all climates 

 where they are produced. 



