168

Then mr. Hooke produced a Discourse or animaduersion of mr
Cassinj vpon the obseruation of mor. Gallet of the passage of
vnder the Sun. wherein he compared this obseruation wth
that of Gassendus in 1631 and that of mr Heuelius in
1671 from wch he makes seuerall conclusions concerning the
motion of the nodes and the Inclination of the orbits of
to that of the Ecliptick _

vpon this occasion seuerall Reflections were made vpon
that obseruation of mr. Gallet of the ouall figure of
mercury appearing in the Sun. mr. Henshaw supposed it
might proceed from the refraction of an atmosphere
about . mr. Hooke conceiued that the body itself of
mercury might be of such a figure, and that it might
proceed from the velocity of its whirling Round vpon
its Axis. he supposing that the Axis of its vertiginous
or Diurnall motion might lye north and south or
at Right angles wth. the /seeming/ motion of it parallell to the aequa
tor, that that he supposed that a very swift vertiguous
motion on that Axis did make the body of somewt of the
shape of turnep or of a solid made by an ellipsis turned
round vpon its shorter diameter and Explaind this
his hypothesis by the shape that a hollow globe of -
glasse will readily Run into if it the pantillion or pipe
at the end of wch. it is fastened be whirled round
very swiftly. And the reason he conceiued why it must
needs be turned round very swiftly was by reason of
its neernesse to the sun, whereby the superficiall parts
would be burnt were it not for the swiftnesse of its motion

Here by the By mr. Hooke explaind his way which
he had formerly deliuerd to mr Oldenberg of making
vse of glasses of any Length wthout a tube the way
of wch. was as followeth

Ref: CELL/RS/HF_170  © Centre for Editing Lives and Letters