US8930A - Improvement in lightning-rods - Google Patents

Description

UNITED STATES PATENT Ormea .M -uns senz-rrr, ortoNeI'NNi/tfrr, 0111o.

nvlPeovEn/IENTlNlLi-GHTNING-Roos.

Spwii'cation forming` part of Letters Patent No. 5,930, lated May 4, 1852.

Be it known that l, JAMES SPRATT, of Gincinnati, in the county ot Hamilton and State of Ohio, havev invented new and useful'lmincrements in the lPoints ol' Liglitning-ltods,

t of' which the tol-lowing` is a specification.

'ihe object ol' my improvenientsis to provide a ainst the destruction ot' lightning-rod points bg; melting, as they not unfrequently do, i'roin the sudden overcharge of thc electric current.

Having', in the course ol' several `vears perience in the manufacture and setting up ot' lightning-rods, frequently observed instances ol" destruction ot' the points bylig'htniug", and recollecting" that some time previous a'point Vformed ot' successive layers ot' iron, brass, 'and tin, which l had set up in an isolated position for experiment7 beingl soon alter; struck by lightning, the outereoveringot' tin melted ott', leaving the brass entirely unaffected 5 and subsequently, during the same season, receiving another shock, the brass was melted oli' from the iron, which, in its turn, was also left entire, Tuvas led to the plan ot' forming;1 my points ot a number of metals ineased one within another, the most fusible to the eutside. The ett'ect of this arrangement is that the fusing action of an excessive shock oflightning is confined to the outer metallic layer or continu; which in flowing` may be said to carry C! the electric tluid with it, or rather perhaps it receives in the act ot' mel tin g ail-accession to its conducting powers; but Whatever may be the true seientic solution ot' the vphenomenon, the fact is demonstrated by experience th at at'- ter the melting' of one layer the next below it is left unscathed and perfect. Thus, by means of a sufllcient numberoflayers-say from three to lfour-a point may be made capable of surviving as many extraordinary shocksras anyT one point is likely to encounter, at least during the existence of any kind of rod such 'as now in use.

The number ot` layers mayvary from two to three, or upward, according to the desired completeness of the instrument, but the fol lowing I have found suitable: The innermost point may be of steel, which may be inc-used in brass,the brass in zinc, and, lastly, 'the zinc may be coated with the alloy' of platinum, silver, &c., formerly patented by me, which Vis a superior' conduct-ing medium, and capable ot' receiving' and preserving; a high finish. Each layer should be about from one-sixteenth to oneeighth of an inch thick, and mar be cast onto the preceding one.

In the annexed drawings the rod' is shown in section, manufactured as above described.

Having thus fully described the nature of my improvement, whatclaim therein as new, and desire to secure by Letters Patent, is-

The formation ot' the point of a lightningrod, ot' three or more metals, incased one within another, the most fusible to the outside, in or der to prevent the destruction ot' the entire point by melting from an overcharge of the electric fluid.

In testimony whereof I have hereunto set my hand before two subscribing witnesses.

'JAMES SFRATT.

NVitnesses Gno.- H. KNIGHT, EDWARD H. Karene

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