COSMOS, VOL. II - World eBook Library

550 COSMOS.
The enjoyment of a long peace might certainly have led us
to expect, that the union under one empire of extensive countries
having the most varied climates, and the facility with
which the officers of state, often accompanied by a numerous
train of learned men, were able to traverse the provinces,
would have been attended, to a remarkable extent, by an
advance not only in geography but in all branches of natural
science, and by the acquisition of a more correct knowledge of
the connection existing among the phenomena of nature : yet
such high expectations were not fulfilled. In this long period
of undivided Roman empire, embracing a term of almost four
centuries, the names of Dioscorides the Cilician, and Galen of
Pergamus, have alone been transmitted to us as those of
observers of nature. The first of these, who increased so con-
is far
siderably the number of the described species of plants,
inferior to the philosophically combining Theophrastes, whilst
the delicacy of his manner of dissecting, and the extent of his
physiological discoveries, place Galen, who extended his
observations to various genera of animals, " very nearly as
high as Aristotle, and, in some respects, even above him."
This judgment embodies the views of Cuvier.*
Besides Dioscorides and Galen, our attention is called to a
third and great name that of Ptolemy. I do not mention
him here as an astronomical systematise!*, or as a geographer,
but as an experimental physicist, who measured refraction,
and who may, therefore, be regarded as the founder of an im-
portant branch of optical science, although
claim to this title has been but recently admitted. f
* Cuvier, Hist, des Sciences naturelles, t. i. pp. 312--328.
1
i Liber
his incontestible
However
Ptholemei de opticis sive aspedibus; a rare manuscript
of the Eoyal Library at Paris (No. 7310), which I examined on the occasion
of discovering a remarkable passage on the refraction of rays in
Sextus Empiricus (adversus Astrologos, lib. v. p. 351, Fabr.). The
extracts which I made from the Paris manuscript in 1811 (therefore
before Delambre and Venturi), will be found in the introduction to my
Eecueil d 'Observations astro nomiques, t. i. pp. Ixv.-lxx. The Greek
original has not been preserved to us, and we have only a Latin translation
of two Arabic manuscripts of Ptolemy's Optics. The name of the Latin
translator was Amiracus Eugenius, Siculus. Compare Venturi, Comment,
sopra la storia e le teorie deW Ottica, Bologna, 1814, p. 227;
Delambre, Hist, de IAstronomic ancienne, 1817, t. i.p. 61, and t. ii. pp.
410-432.