Mf* ti§zt hath alfo taken greif ^are, and at his owa 
Gharge% to h^eall the WigHres&nt\y Etched upon 
jyir Plated. The whoM^fmprefSoD, mtcnded fo^ 
curious, confifts but of 150 Copies. 
IV. EPISTOLAINVITATORIA, 
Ad-^ Ohfirvatioms Magnetics Variationis^ commum S-fndio' 
junBisque Uborihus injiiiuendas. Dat, Altorfi Morkorum 
Jridh Fejii fafchalis^ i68t. 
DR. SturmiusMathem. Profellbr at Altorfi the Au» 
thor of this Letter, herein firft takes notice of the 
feveral fleps by which the Dodrine of the Magnet, hath 
been advanced to its prefcnt State. That its Power of at« 
tra^tiog Iron, hath been taken notice of beyond al! 
Jiorj. But that its verticity to the Poles^ was firft obferved 
about 4c o years (ince by our Countryman Roger Bacon. 
That it gives the fame vertue to Steel, ( whence the In- 
veotion. of the Needk .between 300 and -400 years 
fincej by the Italians. The various Delineation of the 
Needle from the Mertdianm variousPlaces^by SehaBianus^ 
Cahottuf. The Inclination hereof to the nearer Vole^ by 
our Countrymao Robert Norman* And that within thefe 
few Years, the Variation of the Decliaation, and that iti 
one and the fame place5hath alio been taken notice of by 
Mx.Hevelius^ A^^zout^Fetit^Vokkamer^ andotherSa 
Upon coofideratioa whereof, and for that it feemsby 
the Obfervatioos mentioned, that the (aid Variation be° 
iog regular! y made, depends o,ot, according to the Con- 
jefture ot Des-€artes^\i^oxi the Earth,its being, tnore Irony 
Qt Magneiickjit^ fome places,thaa in others 3 nor upon any 
other irregular Gauft : he here Incites the Ingenious in 
all Country s, tagive their joynt afSftance, for the bring- 
ing this Point to a certainty^ From whence we may rea- 
fonably expeft, amongft other part!colars5greatfaprove- 
ments in thefe two, Navigation and Geography. 
