96

whether they were oualls of one kind. The Curator was therefore desired to Diuise some way whereby this -
matter might be determined [grew 2 microsc. 2 of walnut 2 of Hazell. 8th volume of transact. Cyder graffts
[In margin]70   March. 19. 1674. mr Hooke gaue an account of a theory for finding the variation of a Magnetick
needle all ouer the World, which he sayd he knew not whether it were coincident with that of Mr Bond
who many years agoe had pretended to know such a theory whence he also would Deduce the Longitude
The substance of this theory is. That the magnet hath its peculiar poles Distant 10 degrees from the poles
of the Earth about which it moueth soe as to make a Reuolution in 370 years, whence the variation
hath altered of Late about 10 or 11 minutes euery year and will probably continue soe to Doe for some
time till it begins to grow slower & slower & will at Length be stationary & Retrograde and in pro
babilty may Returne. But whether it be soe or not whether it does proceed in a meridian or in a
parallell or great circle or any other irregular Curue, and if a curve whether its concaue or convex
sides be towards vs, more time & obseruations must make cleer, but it seems most probable by com
parting seuerall declinations obserued by Capn Iames & others, that the progresse of this magnetick north
pole is from west to east beyond the north pole. The same proposed the making of an easy & nice
instrument therby to obserue exactly the Variation of the Variations of the needle in many different
parts of the World. He was desired to gett it made. [Muller's letter about Key of chinese Language -
[In margin]72   March. 26. Mr Hooke Repeated his Discourse of the Last day, concerning an hypothesis for soluing the phenome
-na of all the Variations of the magneticall needle all ouer the world. as also his purpose of preparing an easy
& accurate way to be sent abroad for making exact magneticall obseruations. He was desired to begin himself
by making good obseruations of the needells variation here & in order therevnto, to fix a certaine meri
dian at Gresham Colledge, which he vndertooke to doe by the north starr. [Dan Coxes paper concd the
the Extracting volatil salt of vegetable he had had it 8 years R Boyle witnesse -
[In margin]73   Apr. 2. The Curator shewd some Expts. concerng. the various ways that the magneticall effluuia doe bend
and reflect themselves by putting diuers streight steel barrs to the pole of the magnet, some shorter some
Longer, some close to it, some at a distance some in direction some croswise, the effect whereof was
that the filings of Iron being strewed by gentle knockings of the extended parchment ranged themselues
into Oualls or curue figures about the barrs but in a quite differing forme from what they would haue
Receiued had those barrs of Iron been Loadstones of the like shape, that is the poles seemd to lye in thease
where the aequinoctiall would haue been in the /a/ Magnet and the aequinoctialls of these would haue been the
poles of Loadstones of like shape. He promised to prosecute these expts. by applying bodys of Iron
of other figures to the terrella. He mentiond also that whereas a Loadstone would attract a Red
hot iron, steel would not at all respect it [Grew draught of pear & plum tree. [Lister of Stone like
gold in animalls.
[In margin]84.   Apr. 23. Mr. Hooke shewd by a microscope the inward texture of a Bullrush consisting of pipes interwouen
from one end to the other in the manner of a Hurdle or Resembling loose needle work - The same made an Expt to dis-
couer whether a Barr of steel toucht by the immediate contact of a Loadstone would more strongly moue to
it then vntoucht. It was found that the steel suspended at a ballance and counterpoised when thus toucht bore
the same weight when vntoucht. -- Mr. Hooke produced a quadrant with Telescopicall sights wherein
[In margin]qr.   appeard the preeminence of such sights aboue the comon dioptras. [Heuelius of Keplars manuscript & ^/of/ his Di-
optras, alledging difficultys in the vse of telescopicall ones, of Wasmuths Astro: Theory: of a meteor. of the French finding noe
paralax in .] ^ /to/ The Last part of this Letter Mr Hooke sayd, it was desirable to know by what method the french had
made that obseruation of the parallax hauing noe Parallax at all, that was perswaded if the observation
were made with telescopicall sights, some though a very small parallax of the sun would be found. And that by
the naked eye be the instrument never soe accurate one cannot obserue to lesse then a minute, whereas that pa-
rallax will hardly perhaps amount to a quarter of a minute.
[In margin]76.   Apr. 30. the Curator Excused himself that the quadrant formerly promisd was not yet Ready, It was tryd by the same
whether an iron ring will be kept by any magneticall vertue be kept in a posture encompassing the terrella of equall Dis
tance, and it was found upon making seuerall essays with the said Ring that at Length it rested about the terrella vnmoued
Lying vpon a boord in water. this was experimented to see whether we can finde here below, any thing analogous
to the Circle that is about Saturn. It was suggested to make Expts. to finde. 1. whether all parts of the terrella haue
an attraction directly towards it center. 2 whether if there be any such attraction, that attraction be in all places of the
terrella of aequall strength i.e. in the aequator as strong as in the axis. 3. having by tryalls found what the approaches
of magneticall bodys to the magnet, are, according to the Different position of the magnet, perpendicular horizontal
and oblique: to indeavour to find out, since the approaches are made in a curve line, what kind of curue it is.
Mr Hooke suggested that the best dipping needles may be made in Water, because the water taketh off the gravity
as also that a pipe of iron should be made of aequall grauity wth. water Dipping. (nonsens) [Wasmuths paper read
he solues coelestiall motions by spirall lines] mr Hooke Intimated, that that hypothesis was not new. My Ld Bacon ha
uing vsed it in his opuscula. [oldenburg also named Guarinj. -
[In margin]78   Iune. 4. Mr Boyles excellency of the mechanicall hypothesis. Euelyns nauigation & comerce. 2 books of Bocconj] Discourse
read of DD Cox of Vitrioll. -- mr Hooke being calld vpon for his new astronomicall quadrant said that he hoped it
would very shortly be finished, and being desired by the company to acquaint them with the performances to be Expected
from this Instrument, he answered. That it was a quadrant soe contriued as to doe what could be required from
any astronomicall instrument, the particulars whereof he Intended shortly to ^ /publish in/ print. He was desired to hasten the
finishing of soe noble & soe vsefull an Instrument, and to gett it Ready if possible against the next Day. The same
was put in mind of proposing such Expts. as might determine those particulars by him suggested apr. 30.
[In margin]80   Iune 18. the Society adiournd. In the mean time the councill should consider of a way for prosecuting the Work of the Society with
more vigor than hath been done of Late.
Nouemb. 12. Wallis tract of Grauity read. [it being said that the nature of springinesse would contribute to the vnderstanding of
the nature of the Air. Mr Hooke said that he had considerd tht subiect and particularly to make a springy body out of a body not springy

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