of Gilbert the years 1170-80 to 1230. This discrepancy of twenty-five
or thirty years between the views of two competent and unprejudiced
investigators, as a mere question of erudition and interpretation,
is perhaps scarcely worthy of prolonged discussion. But as both
biographers argue from substantially the same data, the arguments
reveal so many interesting and pertinent facts, and the numerous
difficulties attending the interpretation of these facts, that
some comparison of the different views of the biographers and some
criticism of their varying conclusions may not be unwelcome.

[Footnote 1: In Leslie Stephen's "Dictionary of Biography."]

[Footnote 2: _British Medical Journal_, Nov. 12, 1904, p. 1282.]

In the first place then we must say that, as Gilbert is frequently
quoted in the "Thesaurus Pauperum," a work ascribed to Petrus
Hispanus, who (under the title Pope John XXI) died in 1277, this date
determines definitely the _latest_ period to which the Compendium can
be referred. If, as held by some historians, the "Thesaurus" is the
work of Julian, the father of Petrus, the Compendium can be referred
to an earlier date only.

Now Gilbert in his Compendium (f. 259a) refers to the writings of
Averroës (Ibn Roschd) regarding the color of the iris of the eye.
Averroës died in the year 1198. There is no pretense that Gilbert was
familiar with the Arabic tongue, and the earliest translations into
Latin of the writings of Averroës are ascribed by Bacon to the famous
Michael Scot, though Bacon says they were chiefly the work of a
certain Jew named Andrew, who made the translations for Scot. Bacon
also says that these translations were made "_nostris temporibus_,"