استرلاب (_Asturlab_), although found in Masudi[150] and the “Arabian Nights,”[151] is not a genuine Arab word. It was borrowed from some other language by the Arabs, who possessed few or no scientific words of their own. The “Nihayet al-Adab” tells us (in Lane’s “Arabic Dictionary,” under _asturlab_) that the names of all instruments by which time is known, whether by means of calculation or water or sand, are foreign to the Arabic language. In most Arabic dictionaries _asturlab_ is derived from the Greek ἀστρολάβος, a word which appears to go back no further than the second century B.C., when it was employed by the Egyptian astronomer, Ptolemy. But it was long suspected that the instrument was of eastern origin,[152] and all doubt about the matter was at length set at rest by Mr. George Smith’s discovery, in the palace of Sennacherib at Nineveh, of the fragment of an astrolabe,[153] which cannot be dated later than the eighth century B.C. Now the earliest recorded astronomical observation made by the Greeks was the determination of the summer solstice by Meton, 430 B.C.[154] For the name of this fragment, therefore, we must look to the language of the country of its birth; and there we find the Persian _asturlab_, which is apparently formed from the primitive verbal root _labh_ = taking,[155] and the Persian _astar_ or _sitára_ = Pehlevi, _çtârak_ = Zend, _çtare_ = Sanskrit, _star_ = our own _star_. The Arabs most probably took their _asturlab_, with so many other words, from the Persian. The Greeks who followed Alexander the Great into Persia found there much that was new to them. They saw for the first time “the cotton tree and the fine tissues and paper for which it furnished the materials.”[156] They handled the wool of the great Bombax tree. They found naphtha, of whose properties Alexander was entirely ignorant.[157] They obtained drugs and gums of which they knew nothing. The philosopher Kallisthenes discovered in Babylon Chaldæan astronomical observations extending back to 721 B.C.;[158] was shown, we cannot doubt, the instrument with which they were made; and probably heard for the first time the word _asturlab_ or _usturlab_. For copper (or some alloy of it[159]) the _cyprium_ of Pliny (which became _cuprum_ about the end of the third century A.D.) is ignored in the tract, and the metal is called _æs rubicundus_. This phrase may possibly represent the χαλκὸς ἐρυθρός of Homer (Il. ix. 365); but it is far more probably the literal translation of the Arabic phrase used to this day for copper نحاس احمر (_nuhas ahmar_) = red brass.