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nou: 27 RH shewd an attempt to make a body soe thin that when euacuated
it might swim in the air. mentiond Lana & his book -
Dec: 4. RH swed Expt. of the springiness and bending of cole by heat. as also
of glasse pipes - Dec: 11. RH brought in an apparatus to shew by expts.
the strength of Loadstones attraction, and in wt proportion at seuerall Distances.
the apparatus orderd to be fitted. Sr. W Petty moued that there might be a con
stant apparatus of Instruments for expts. of motion opticall magneticall
electricall mercuriall - Dec: 18. RH produced his Instrument for trying the
force of Loadstones but wthout effect.
Ian: 15. 1673/4. RH Shewd expt of a diuided Ruler placed at a Distance by
wch. he manifested that noe eye could distinguish a lesse angule then a minute
and consequently all nicenesse in mathematicall Instruments beyond that vaine
Ia: 22. RH proposd to make a new Astron: quadrant. he related it would
cost 10ll. orderd to make one of that price. Last Days Expt. of sights repeated
wth successse. Feb: 5. RH producd a new reflecting telescope to look
Directly at the object & see it erected. tis mentiond in mersennus & Gregorys opticks
Feb: 12. RH made seuerall tryalls to find whether the strength of the Loadstone
would be alterd by the interposing seuerall bodys, he was orderd to try many
of these expts. by himself.
Feb: 19. RH tryd many more expts. wth the Loadstone by interposing. RH producd
a quadrant of 4 inches inches Distinguishing to minutes wth telescopicall sights -
It was mr Boyles. call on for his other quadrant -
Feb: 26. RH shewd the Lines of Inclination to the Axis of the terrella. by dust
of on a Drum of Drumhead of parchment wth a round hole through it. he vrgd
that they were oualls whose Longer axis was at Right angles wth. the Axis of the
stone and in the middle between the poles that they were quite contrary to Des
cartes Theory. mouing the stone vnder the parchment mad the Dust Rise and therby
the parchment seemd as twere transparent. many Expts. about the attraction of
cappd & vncappd stones. march. 5. The same & seuerall other magne
ticall Expts tryd by RH march 12. RH shewd Experiment of poising a
Loadstone soe as to turne it self N & S. . RH. intimated a theory for finding
the magn: variations ouer the world & promised to make a Rule for that pur
pose. RH desird to diuise a way for Determining the ouall lines of Inclinatio
whether they be all of one kind. march: 19 1673/4 -
RH gaue an account of a theory for finding the variations of the magnetick needle
all ouer the world which he said he knew not whether it were the same wth 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 was that
the magnet hath its peculiar poles Distant about 10 degrees from the pole
of the earth about wch. it moueth soe as to make a reuolution in about
370 years. whence the variation hath alterd of Late about 10 or 11
euery year and will probably soe continue to doe for some time till it
begin to grow slower & slower & will at Length be stationary & Retrograde
and in probability may returne. but whether it be soe or not

Ref: CELL/RS/HF_s02  © Centre for Editing Lives and Letters