371

Decemb the 4. 1679.

before the meeting 5 of the Councell vizt. mr. Henshaw mr. Hill Sr. I Hoskins Sr. I Louther
and mr Hooke vieud the Gallery. and appointed mr Hunt to set vp a partition for the library
at the west end next the Door to inclose it for a Library. -

mr. Henshaw vice president tooke the chair.

The Experiment propounded the Last Day by mr Hooke to shew that Copper &
tin being melted together into one masse would make a compositum
extremely Differing from them both, was tryed And examined and It was
found that equall parts of Copper & tinn melted together Did make a mettall wch
was exceeding hard & very brittle whereas the ingredients are both very soft
& very malleable and whereas copper is of a very brown Red colour this was
exceeding white, and which was the Principall propriety it had newly ac=
quired the Grauity thereof was found to exceed both Copper and tin in their
specifick grauity. for whereas Copper to water is as 8 1/3 to 1. and Tin
to water as 6 4/5 to 1. and thence the compositum ought to haue been ^/to water/
as 7 17/30 to 1. It was found that by weighing a part of this substance
first in the air and then in the Water that the weight thereof to water
was 8 198/266 or 8 3/4 to 1. for It weighed in the air 2326 grain[es]
and in the water 2060 graines -

Hereupon the cause of this was Explaind by mr. Hooke & ascribed
to the penetration which those bodys made into one another, and
It was illustrated by the Experiment that had been formerly
produced here of the mixture of Water & Oyle of sulphur
or vitrioll-
These experiments were made in order to Illustrate some Theorys
about the pressure of the Atmosphere to shew how the air might
be impregnated wth other bodys whereby the specifique grauity thereof
might be augmented & altered the height thereof remaining the
same.
mr. Flamstead was of opinion that the Leauity of the air proceeded on
ly from the motion of the air and the grauity thereof from its
standing still and that the same body moued did not presse soe much
as when it stood still, vpon wch. seuerall things were debated -
Mr. Hooke alledged seuerall obseruations he had made which were contra
ry to that supposition, for he had found that after a long and still rain
during all wch. the mercury had continued to fall soe soon as euer
the air began to moue & the wind to blow the mercury presently
began to ascend. tis true that it often happens that in Great Winds
the Mercury is very Low. And soe it is also when there are noe
winds at all stirring as in Great Raines. And tis noe new obseru
tion that in Stormy weather the Air is light the Barometers being all soe Mar
ked

Ref: CELL/RS/HF_373  © Centre for Editing Lives and Letters