326 THE FARMER AT HOME. 



more than three months for each ; whereas the same number of 

 Academicians, the one half belonging to the Academy of Sciences, 

 and the other to that of Belles Lettres, give only 10,511 years of life, 

 consequently 69 years and a little more than two months for the 

 mortal career of each. It is therefore not improbable, that in the 

 ages of patriarchal innocence, the period of 150 or even 200 years, 

 was much more commonly attained than it is in our times. 



PERSPIRATION OF PLANTS. In vegetable physiology, takes 

 place chiefly from the surface of their leaves. In order to collect the 

 liquor perspired, it is only necessary to introduce a branch of the plant 

 into any sufficiently capacious glass vessel ; when the fluid which 

 exudes will trickle down the sides of the glass, in great abundance, 

 especially if the experiment be made in sunshine. The liquor thus 

 obtained is of a clear watery nature, scarcely distinguishable to our 

 senses, or to our chemical inquiries, from the sap of the same plant, 

 whatever it may be, procured by wounding its branches before the 

 foliage expands. This, which may be termed insensible perspiration 

 of plants, becomes in some cases sensible ; as when it runs down, like 

 a slight shower, from willow or poplar trees, in hot sunny weather ; 

 or when it collects in drops on the leaves of plaintain trees in a stove. 

 Hales and others have made experiments to ascertain the quantity of 

 insensible perspiration in various plants. The great annual sun- 

 flower was found to perspire about seventeen times as much as the 

 ordinary insensible perspiration of the human skin. The Cornelian 

 cherry, Cornus mascula, is said to discharge, in twenty-four hours, as 

 much fluid as is equal to twice the weight of the whole shrub. Suc- 

 culent leaves perspire much slower than others, though they absorb in 

 a far more rapid proportion. 



This watery perspiration is the only excrementitious discharge of 

 the vegetable body. The sap being carried up into the leaves, where 

 it is acted upon by the air and light, for the most important purposes, 

 yields those various and highly curious secretions, which, being; carried 

 down into the bark, afford matter for the increase of the tree, as well 

 as for the manifestation of its various qualities. The great bulk of 

 the sap which remains, as it does not return to the root, like the blood 

 of animals to their heart, can be disposed of no otherwise than by a 

 copious evaporation. Dr. Darwin was of opinion that this watery 

 perspiration rendered a further service to the plant, by being acted 

 upon by light, so as to give out oxygen, which was immediately ab- 

 sorbed by the air vessels. 



PEWTER. A factitious metal used in domestic utensils. It is 

 very uncertain in its composition. The common utensils of the lowest 

 price, are made from an alloy composed of about twenty of tin, three 

 of lead, and one of brass. The lead is of no use but to make it 

 cheaper, and doubtless on this account is often used in larger propor- 

 tion. The brass is intended to give stiffness and hardness, the tin 



