THE PAST AND FUTURE OF ALUMINUM. 399 



Under more extensive manufacture the metal has been studied 

 at ease, and its physical and chemical properties have been ex- 

 actly determined. It is silver-white, but little changed by the air, 

 which gives it a slightly bluish tinge except when it contains 

 iron. Its most striking quality, and one which makes it most 

 suitable for a large number of industrial applications, is its light- 

 ness of weight. Its density varies from 2'56, when it is in a mol- 

 ten condition, to 2'71, when its particles have been consolidated by 

 hammering, and its mean density may be put at about 2'60 that 

 is, it weighs about two and a half times as much as water, while 

 steel is nearly three times as heavy, and copper three and a half 

 times, silver four times, and gold nearly eight times ; so that four 

 times as many articles can be made from a given weight of alumi- 

 num as from the same weight of silver. In many cases one metal 

 may be substituted for the other without inconvenience. While 

 not so hard as gold or silver, aluminum is equally malleable and 

 ductile : it can be beaten into thin pellicles that a breath will blow 

 away, with which objects can be aluminum-coated as they are 

 gilded. It can be drawn into wires finer than a hair, and yet so 

 firm and supple that they can be woven with silk. It is less fusi- 

 ble than zinc and more so than silver, and is easy, therefore, to cast 

 and mold. Although very sonorous, it has not yet been success- 

 fully cast into bells, because the repeated strokes of the hammer 

 make it hard and brittle ; but the tuning forks made from it are 

 satisfactory to musical artists. The sulphurets, which blacken 

 silver so quickly, are without action on aluminum. Similarly in- 

 sensible to organic secretions, it lends itself to the making of cer- 

 tain surgical apparatus. Ingenious tubes have been made from 

 it which permit patients who have been operated upon for tra- 

 cheotomy to breathe, and American dentists have utilized it in the 

 construction of their modern apparatus. It is equally fitted for 

 making into plate and kitchen utensils, for which its specific 

 lightness makes its use convenient. Its conductibility for both 

 heat and electricity authorizes us to predict a fine future for it. 

 It is, it is true, an inferior conductor to gold and silver, about 

 as good as copper, and twice as good as iron ; hence an aluminum 

 wire will carry twice as great a quantity of electricity in a given 

 time as an iron wire ; or, to carry an equal quantity the aluminum 

 wire need be only half as large ; and aluminum being only one 

 third as heavy as iron, it will have to be only one sixth as heavy. 

 These properties should, were the cost equalized, make aluminum 

 vastly more available for telegraphic and other electric wires than 

 iron. Furthermore, aluminum not being acted upon by the air, 

 galvanization, which is necessary for the preservation of iron 

 wire, could be dispensed with. 



Aluminum is, however, inferior to iron and steel in tenacity, 



