800.] On extending the Uſe of Tinned- Iron. 174

eight yeárs war, has been expended in Europe in the bullét and cannon foundery, and in all other branches of armoury, may well zccount for a ſubſequent ſcarcitv, and(conſequently) an en- hancement in the price of theſe metals.

Be chat as it may, it is cleârly an obje& of the firſt impor- tance to examine into the poſlibility of /uéftituting tinned-iron for copper for znany purpoſes; and for the longer preſervation of iron in ail its preſent applications, which are not expoſed to a heat ſufficiently violent to fuſe the tin-coating. It does not appear that any ſcientific experiments have been made on this ſubje@; and the utility of the tin-plate worker's art has been thus long apparent without any extenſion of its application. The moîft wonderful abſurdity is, that moſt of the purpoſes for which tinned-iron is in uſe, are preciſely thoſe for which it is unfit, in veſſels intended to be ſet on fires, which immediately bare the iron of its tin,:

As thoſe acids(whether ærial or aqueous) which readily calcify iron, become more and more acceſſible by the improve- ments of modern chemiſtry, it is not now impoſible. to cal- culate and apply the corroding action of years in a moderate time on any given ſubſtance, and it.remains rather to enumerate the advantages of ſucceſsful experiments, than to ſuggeſt any ſeries which might be concluſive on this point of knowledge.

Tt is known that the tenacity of the ſtrength of iron, is to that of copper as five to three; wherefore, in all ſubſtitu:ions of tinned-iron, the bulk of the article would be diminiſhed as three to five. In the caſe of the bolts of ſhipping, this coù- ſideration is of ſome importance; and, in al! caſes, the intro- dudtion of tinned-iron might ſupplant the preſent faſhion of uſing braſs in many of the purpoſes of life.

But a much more extenſive benefit would be effe@uated, if, inſtead of confining the application of tin to iron-plates, ail” other applications of iron were guarded with tin: thus would iron work become as durable as it is uſeful.‘To enumerate the’ articles to which tin might be advantageouſly applied, would be almoſt to catalogue the ironmonger’s ſhop.‘The fmalleſt nails (tin tacks) are already tinned; the larger nails, hooks, in a word, every thing up to the heavieſt anchor; might be improved 1n the ſame manner, except thoſe indeed which muſt be expoſed 2 the grindſtone or the fre, thât is, edge-tools, pokers, boilers,

GS

Biſhop Watſon has related a fa whieh ſeems to indicate an abſolute incorporation-of the two metals in the ad of tinning iron.‘If this be thought an ualikely fa, it is certainly worth examination in the laboratory, as coming from ſuch reſpeGable chemical authority, and promiſing ſuch vaſt utility of applica- tion. However, without this incorporation, the affinity of the two metals is certainly ſo potent, that carefully repeated tin- nings will reſiſt the corroſion of the air for a century.