Physicians at London. His _De Magnete_ was the first noteworthy treatise
on physics printed in England. He treated of the earth as a spherical
magnet and suggested the variation and declination of the needle as a means
of finding latitude at sea.

[92] The title says "ab authoris fratre collectum," although it was edited
by J. Gruterus.

[93] Porta was born at Naples in 1550 and died there in 1615. He studied
the subject of lenses and the theory of sight, did some work in hydraulics
and agriculture, and was well known as an astrologer. His _Magiae naturalis
libri XX_ was published at Naples in 1589. The above title should read
_curvilineorum_.

[94] Cataldi was born in 1548 and died at Bologna in 1626. He was professor
of mathematics at Perugia, Florence, and Bologna, and is known in
mathematics chiefly for his work in continued fractions. He was one of the
scholarly men of his day.

[95] Georg Joachim Rheticus was born at Feldkirch in 1514 and died at
Caschau, Hungary, in 1576. He was one of the most prominent pupils of
Copernicus, his _Narratio de libris revolutionum Copernici_ (Dantzig, 1540)
having done much to make the theory of his master known.

[96] Henry Briggs, who did so much to make logarithms known, and who used
the base 10, was born at Warley Wood, in Yorkshire, in 1560, and died at
Oxford in 1630. He was Savilian professor of mathematics at Oxford, and his
grave may still be seen there.

[97] He lived at "Reggio nella Emilia" in the 16th and 17th centuries. His
_Regola e modo facilissimo di quadrare il cerchio_ was published at Reggio
in 1609.

[98] Christoph Klau (Clavius) was born at Bamberg in 1537, and died at Rome
in 1612. He was a Jesuit priest and taught mathematics in the Jesuit
College at Rome. He wrote a number of works on mathematics, including
excellent text-books on arithmetic and algebra.

[99] Christopher Gruenberger, or Grienberger, was born at Halle in Tyrol in
1561, and died at Rome in 1636. He was, like Clavius, a Jesuit and a
mathematician, and he wrote a little upon the subject of projections. His
_Prospectiva nova coelestis_ appeared at Rome in 1612.

[100] The name should, of course, be Lansbergii in the genitive, and is so
in the original title. Philippus Lansbergius was born at Ghent in 1560, and
died at Middelburg in 1632. He was a Protestant theologian, and was also a
physician and astronomer. He was a well-known supporter of Galileo and
Copernicus. His _Commentationes