ee se 
XXXI. Description of a Burning Mirror, ly means of 
which we may reflect and fix on any Object, whether at 
Rest or in Motion, the solar Rays in as great a Quantity 
as we please. By F.PEYRARD, Professor of Mathematics 
in the Bonaparte Lyceum. Translated from the French. 
[Continued ftom p. 146.] 
My mirror is exempt from all these defects; for, in pro- 
portion as the sun advances; the glasses do not cease to 
forma parabolic mirror, the axis of which is constantly di- 
rected to the sun’s centre, passing by the object which we 
wish to inflame: @. e. at each instant my mirror changes its 
-form in order to produce its effect. 
Before Buffon, Athanasius Kircher contrived a mitror for 
burning at 100 feet and upwards. His mirror was a col- 
lection of plain and circular glasses; he placed them on a 
wall, giving them a proper inclination, in order that the 
images of the sun might be reflected on the same object. 
Athanasius Kircher made his experiments with five glasses 
only: he informs us that the heat produced with four glasses 
was still supportable, and that the heat produced with five 
was almost insupportable. ‘+I am of opinion,” he adds, 
‘* that it was with plain mirrors thus arranged that Proclius 
burned the ships of Vitalien.”’ ; 
Kircher did not push his experiments further, and con- 
tented himself with inviting the learned to repeat them with 
a greater number of glasses *. ‘uk 
it is almost unnecessary to observe that the above has al] 
the defects of Buffon’s mirror, 
Anthemius de Tralles, who flourished about the end of the 
fifth century, and was intrusted by Justinian the First, 
with the building of the temple of St. Sophia at Constanti- 
nople, also contrived a burning mirror. A fragment of his, 
position of the earth into like strata or layers of matter, commonly through 
vast tracts.” —Phil, Trans, No. 379, or Reid and Gray’s Abridgement, vol. vi. 
$153; $ 
: In consequence also of my inquiries. by the same channel, after the papers 
and maps of the late Mr. Tofield, relating to the British strata, William 
. Smithson, Esq. of Heath near Waketield, procured a letter to be written 
to Mr. William Tofield of Wath-upon Perne. a younger son of Mr. T. ard 
has transmitted me his answer, which unfortunately states, that all his fa- 
ther’s manuscripts were by his elder brother taken with him into Hol'and, 
where -he has resided for 18 years past, and the st te of the war has, for 
some years, prevented any communicaticn with hin.—J F. 
* Kircher De Arle magna lucis et wnlre, lib, x. par.-fig. ii, probl. 4, 
m 
