transmutations to which the devout Mohammedan in the above quotation
alludes.

The Arabians, with all this physical knowledge, do not appear to have
been in possession of the thermometer, though they knew the great
importance of temperature measures, employing the areometer for that
purpose. They had detected the variation in density of liquids by heat,
but not the variation in volume. In their measures of time they were
more successful; they had several kinds of clepsydras. A balance
clepsydra is described in the work from which I am quoting. [Sidenote:
The pendulum clock.] But it was their great astronomer, Ebn Junis, who
accomplished the most valuable of all chronometric improvements. He
first applied the pendulum to the measure of time. Laplace, in the fifth
note to his Systeme du Monde, avails himself of the observations of this
philosopher, with those of Albategnius and other Arabians, as
incontestable proof of the diminution of the eccentricity of the earth's
orbit. [Sidenote: Astronomical works of Ebn Junis.] He states, moreover,
that the observation of Ebn Junis of the obliquity of the ecliptic,
properly corrected for parallax and refraction, gives for the year A.D.
1000 a result closely approaching to the theoretical. He also mentions
another observation of Ebn Junis, October 31, A.D. 1007, as of much
importance in reference to the great inequalities of Jupiter and Saturn.
[Sidenote: The Arabic numerals.] I have already remarked that, in the
writings of this great Arabian, the Arabic numerals and our common
arithmetical processes are currently used. From Africa and Spain they
passed into Italy, finding ready acceptance among commercial men, who
recognised at once their value, and, as William of Malmesbury says,
being a wonderful relief to the "sweating calculators;" an epithet of
which the correctness will soon appear to any one who will try to do a
common multiplication or division problem by the aid of the old Roman
numerals. It is said that Gerbert--Pope Sylvester--was the first to
introduce a knowledge of them into Europe; he had learned them at the
Mohammedan university of Cordova. It is in allusion to the cipher, which
follows the 9, but which, added to any of the other digits, increases by
tenfold its power, that, in a letter to his patron, the Emperor Otho
III., with humility he playfully but truly says, "I am like the last of
all the numbers."

[Sidenote: Arabian philosophy.] The overthrow of the Rom