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by: he then quite fills the pan with the leather, and places it on a gentle flat [[semi-circle--page number in top right corner]] 100 [[/semi-circle]] fire, covering and surrounding it with charcoal. The pan being brought to somewhat more than a red heat, he keeps it so about half an hour, and then suddenly quenches the bars in a large quantity of cold water.
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From the Philos. Trans. Vol. 47 for 1751 & 1752. p.126.
XVII. [[underlined]]A Letter from the Secretary of the Royal Academy of Sciences in[[/underlined]] Sweden, [[underlined]]to[[/underlined]] Cromwell Mortimer, [[underlined]]M.D et F.R.Sec. concerning the variation of the[[/underlined]] magnetic needle.
Celeberrimo Domino Doctori, et Societatis Regio Londinensis Secretario, Cromwello Mortimer, S.P.D. Petrus Wargentin, Acad. Reg. Scient. Suecico Secretarius.
[[margin--right]]The Northern lights cause a variation of the mgnetic needle.[[/margin]]
Read Feb.21.1750. OBIIT ante paucos menses secretarius Academio Regio Scientiarum Suecico, vir in mathematicis scientiis versatissimus, D. Petrus Elvus: cui, ex decreto academio, ego mox suffectus secretarius, muneris mei esse judicavi, commercium literarium cum exteris societatibus, academiis, et viris eruditis, instituere, cum persuasissimus sim ejusmodi literatorum commercia plurimum ad scientiarum incrementum facere.
**Ut aliquid ad scientias pertinens tibi impertiam, paucis narrabo de observatis a me nuper variantibus quotidie paullulum, sed sope admodum turbatis, declinationibus acus magnetico.
[[indent]] Hälleius vestras dudum suspicatus est, esse quoddam inter lumen boreale et acum magneticam commercium. Id certissimis experimentis et observationibus evicerunt jam aliquot annos Celsius atque Hiorterus, astronomi apud nos, dum viverent, celebres, qui sopissime animadverterunt, acum magnopere turbatam atque inquietam esse, quoties lumen boreale ad zenit, vel ad plagam coeli meridionalem ascendit, ita quidem, ut declinatio videretur sequi motum luminis, et intrapauca temporis minuta totos tres et quatuor gradus aliquando variare. Res fide major mihi initio visa est. Meis oculis tam mirum phonomenon notare cupiebam. Cum itaque mihi traderetur acus, pedem suecanum longitudine oquans, ab opifice nostro ingeniosissimo D. Ekstrom confecta, agilissima; mox, ineunte Februario hujus anni, coepi annotare illius declinationes; quas statim quotidie variantes deprehendi, prout Grahamus, Celsius, etc. antea observaverant, la vidélicet lege, ut acus ab hora septima matutina ad secundam post meridiem, ab oriente ad occidentem magis magisque discedat, interdum tertiam vel quartam partem unius gradus. Post horam secundam iterum reveritur ad octavam vespertinam, usqued [[strikethrough]] ? [[/strikethrough]] ^um eundem fere situm attigerit, quem hora octava matutina. Per totam noctem fere quieta esse solet, saltem non nisi parum circa mediam noctem