The Brass Instrument

Keli ha-neḥoshet, Introduction & Chapter 1

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About This Entry

The title of The Brass Instrument (Keli ha-neḥoshet) refers to the astrolabe, a tool used for astronomical measurements and calculations, thought to have been first invented around the second century BCE. An astrolabe is made up of a circular body, called the mater (mother), which holds removable plates that are engraved with a stereographic projection of the celestial sphere as it appears in the latitude where the astrolabe is to be used. Over the plates sits the rete (net), which indicates the positions of the stars and the ring of the ecliptic and can be rotated. Aside from calculating star positions, the astrolabe can also be used for observations, by sighting an object through the alidade. As Ibn Ezra acknowledges, knowledge of the astrolabe stemmed from Greek writings transmitted by Arabic scientists. He therefore sought to explain this instrument for a Hebrew-reading audience. Three Hebrew translations and one Latin one, which Abraham wrote with a student, survive to this day. The excerpts that follow are drawn from the beginning of the work.

Circular, intricate brass object with Arabic and Hebrew inscriptions, geometric markings, and a rotating arm.

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O living God, let me implore You,

grant aid to Ben Ezra

afflicted in exile.

His soul relies on Your mercy.

May He reveal concealed insight

to him [i.e., Ibn Ezra], establish the work of his hands.

May He show grace to a student who is wise of heart

for thus is His name, let us sing!

Blessed is He who established the lip’s speech

and enlightens the children of Seth.

He taught them number and measurement,

the forms of circle and arc.

And He placed the image of God’s artistry

on the plates and rete.

May the wise of heart come and learn

The Book of the Astrolabe. [ . . . ]

Introduction

The author says: an educated person can translate one language into another only with the greatest difficulty. Even more so with the holy tongue, which we know only from what is written in scripture. Now, this instrument known as the astrolabe, which is in the works of Ptolemy, has many names, and it is mentioned in many languages. I shall acknowledge them to the best of my ability. May the Lord who teaches man knowledge guide my words in the path of truth. I shall elucidate this instrument in thirty-six chapters. May my aid come from the Lord.

Chapter 1

Concerning the instrument [known as the] astrolabe, the names it goes by, and its features.

I call it “the brass instrument,” because they make most of them from brass. But if one wishes to make it from silver or gold, one may do so. An astrolabe has a ring, a throne, a “mother and children” [i.e., mater and plates], a rete, an alidade, and a “horse with its rider” [i.e., wedge and pin]. Now I shall explain each one in its place. The first part of the instrument is the ring. This is the chain on which the instrument hangs. And it is proper for there to be one ring inside another, so the instrument is not tangled up when one picks up the back.

And after that is the throne, in which the ring is fixed, and it protrudes from the mater, and everyone designs it according to their preferences, so as to decorate the instrument.

And after this is the mater, and it is the circular area which is on the outside, such that the plates are within it, and above them is the rete, and behind it is the alidade, and it is called the mater [“mother”] since the rest of the plates are like children to it.

The mater: on its back are two diameter-[lines]. One of them descends from above, from the top of the ring, which is the chain from which the instrument hangs, downward. And the second cuts through the circle from the left side, [given that] the man is holding the instrument in his right hand; the left-hand starting point of the diameter that cuts through the circle is called East. And the right-hand one is called West. And [on] the diameter which descends from the top of the ring downward, the bottom of the ring is called South and that which is above is called North.

Translated by Naftali (Neal) Kreisler.

Published in: The Posen Library of Jewish Culture and Civilization, vol. 3: Encountering Christianity and Islam.