VI. Mcount of fome Experiments tried with 
Mo 7 if.Y'i\\cttes'Burnin^Con£aVe^ mjune 1718. 
(By the ^ev. Dr. J. Harris and Dr. J.T. Defa- 
HIS Miroir is a Concave 47 Inches wide, and 
ground to a Sphere of 76 Inches Radius ; fo 
that its Focus is about 38 Inches diftant from 
the Vertex of the Glafs. Ihe Metal of which it is 
made is a Mixture of Copper, Tin and Tin-Glals, 
whofc Reflexion has fomething of a yellow Caft. The 
Concavc«Surface has Icarce any Flaws, and thofe very 
fmallj but the Convex fide, which isalfo polifli’d, has 
fome Holes in it. 
Having held feveral Bodies in the Focus of this Mi- 
roir, we obferv’d what happen’d to them whilft expos’d 
to this great Heat ; and with an half Iccond Pendulum 
took notice of the Time in which any material Change 
happen’d to them. 
The Experiments were as follow, and made from 
Nine till Twelve in the Morning. 
I . A red piece of a Roman Patera^ which began to 
melt in 3 Seconds, was ready to drop in lOo. 
X. Another black Piece melted at 4, and was 
ready to drop at 64 Seconds. 
3. Chalk taken out of an Echinus Spatagus fill’d 
with Chalk only, fled away in 13 Seconds, 
4. A FoITil e-Shell calcin’d in 7 Seconds, and did 
no more in 64. 
5. A piece of Pompeys Pillar at Alexandria, was 
vitrified in the Black Part in 50 Seconds, 
and in the White part in 54. 6 . Cop- 
guliers, %eg, Soc. SS. 
