oeaaCee 
But this work of the ancient mathematician is fo i - 
and fo inaccurate, that moft perfons have hefitated in 
afcribing it to this celebrated author. ‘The r part of 
aad Pliny. The effets of burning-glaffes were obferved 
by the ancients ; and the power of concave mirrors in this 
refpe& is taken notice of by Euclid in the treatife we have 
mentioned. It has been faid, and very generally allowed, 
that Archimedes tne a treatife on the fubje& of burning 
mirrors, though it be not now extant. From the time of 
id oe repeats the crude fentiments of 
of op d 150 
er Chrift, wrete a treatife of optics, which is loit ; 
ie accounts of others it is known, that he treate d 
P 
of eciawicl refra Afte tolemy there occurs 
a gteat chafm in the hiftory of optics, as well as othe 
ranches 
of mathematics and philofophy, which were cul- 
itis chiefly by the Arabs during the dark ages of 
Europe. The fir Arabian writer of optics, of whom we 
bi, 
o 
more largely on this fubje&t, and who treated diftin@ly of 
iret, reflecte d, and refra&ted vifion, and alfo of burnin 
- The only work of the say pene seme anc 
that .. Sines azen, who fi 
perseet 1 age 
brain. 
aol the heavenly bodies, and that it is the 
caufe of the rete ng of the ftars : 
that neither he nor 
publifhed in 1270. 
his work contains every thing *avable in nas of Alhazen, 
pears much more diftant from us aoe in the oeuths on ace 
count - the intermediate {pace ae a Abe variety 
of obje&ts upon the vifible furface of the earth. He 
scab the twinkling of the ftars to the fiscen of the air, 
in which the light is refraGted ; and he fhews that refraction, 
as well as reflection, is neceffary to form the rainbow. He 
many other obfervations onits phenomena. Vitellio attempts 
te explain refraction, or to afcertain the law of it, and he 
confiders the foci of glafs {fpheres, and the apparent fize of 
objets feen through them ; but Montucla fays, that he is 
not at all accurate upon any of thefe fubje&s. Ten years 
after the publication of Vitellio’s work, Peccam, archbifhop 
of Canterbury, wrote a treatife of dire& optics, which was 
then called perfpeCtive ; but without making any addition to 
the exifting ftock of optical knowledge. His treatife is oes 
to be concife and judicious, and to contain, among ot 
things, a very clear and diftin& account of the reafon ae 
the {ky near the horizon appears more diftant from us than 
at any other place. As contemporary with Vitellio and Pec- 
cam, was Roger Bacon, who frequently quotes Alhazen on the 
{ubject of optics, and who does not feeim, as far as refpetts the 
theory of optics, to have much improved on the Arabian 
writer. From the writings of Alhazen, and Bacon’s ob- 
fervations and experiments, fome monks, it is probable, gra- 
dually fucceeded in the conftru€tion of fpe@tacles. The ufe 
capital improvements in the {cience of optics. This writer, 
in his treatife «« De Lumine et Umbra,” publifhed in 1575, 
demonitrates that the cryftalline humour of the eye is a Jens, 
vances towards the difcovery of the nature of vifion, Jo- 
hannes Baptifta Porta, of Naples, invented the camera ob- 
{cura, an account of which h his ‘* Magia 
egies f. 
teen years 
and renee and ate 
lantern, wei that in the night 
