246 ANNUAL OF SCIENTIFIC DISCOVERY. 



proportion can be effected, whilst with others it cannot ; and hence for the 

 former, we propose to retain the word "alloy," using the expression 

 " combination of metals " for the latter. On this basis, therefore, an alloy 

 will mean a mixture of one or more atoms, or equivalents of one metal, with 

 one or more atoms or equivalents of another, so as to form what may be 

 called a chemical compound, where.as a "combination of metals" will merely 

 imply a mixture in no definite proportions, but suggesting the idea of a 

 mechanical compound : thus, brass formed from 34 parts of zinc and 64 parts 

 of copper, or 34 zinc and 96 copper, would be an alloy, whilst our ordinary 

 silver and gold coinage would be an admixture of metals. 



With this preliminary definition, we will now proceed to examine the few 

 alloys in common use in the arts, or, more correctly speaking, those com- 

 pounds which nearly approach the nature of alloys. In such a list we may 

 place brass, type-metal, bell-metal, speculum-metal, pewter, Britannia-metal, 

 and solder. The first has already been described ; the second generally con- 

 sists of about 5 parts of lead and 1 of antimony, which closely approaches to 

 3 atoms of lead and 1 of antimony. Bell-metal is composed of 4 parts of 

 copper and 1 of tin, and may be regarded as an alloy of 7 atoms of copper 

 to 1 of tin. Speculum-metal contains about equal quantities of copper and 

 tin, with small and variable proportions of arsenic: it may consequently 

 be looked upon as composed of 2 atoms of copper and 1 of tin. Pewter 

 and Britannia-metal are triple compounds of tin, antimony, and lead, 

 in which the proportions approach, for the first, an atom of each ingredient, 

 and for the second 3 atoms of tin, 2 of antimony, and 1 of lead. Solder is 

 more variable than any of the others ; but the best kind is made with 3 parts 

 of lead and 1 of tin, which corresponds to about 2 atoms of lead and 1 of 

 tin. There are other compounds which might, perhaps, have been brought 

 within this group ; but as, in reality, none even of those we have selected, are, 

 strictly speaking, alloys in our limited sense of the expression, it is useless to 

 follow the subject further than to show, by this near approach to atomic com- 

 bination, how probable it is that the same substances, fabricated with a due 

 regard to that proportion, would possess more useful qualities and less fre- 

 quently disappoint the expectations of the artisan. Take, for example, the 

 case of bell-metal, an article notorious for the uncertainty of its results ; this 

 compound contains, according to the caprice of its fabricator, from 12 to 22 

 parts of tin, with from 78 to 88 parts of copper, and a little antimony, arsenic, 

 or even iron : if, however, it requires to be an alloy of 7 atoms of copper and 

 1 of tin, the proper proportions would be 79 copper and 21 tin. With facts 

 of this kind before our eyes, it seems strange that nothing practical has 

 arisen with respect to alloys; and we cannot help thinking that amongst 

 the other elements of the working man's education, the doctrine of definite 

 combining proportions might very properly be included. Engineers' Journal. 



NEW MODE OF COPPERING VESSELS. 



M. Oudry, of France, has made preliminary experiments for applying 

 electrotj^pe on an enormous scale no other than to the coppering of wood 

 and iron ships of whatever tonnage. The vessel would be coated with an 



