, a French mathetician and engineer, was born at Lyons July 24,
, a French mathetician and engineer, was born at Lyons July 24, 1657,
and educated there in the college of Jesuits, from whence
he removed to Paris in 1675. He first made an acquaintance with du Hamel, secretary to the academy of sciences;
who, observing his genius to lie strongly towards astronomy,
presented him to Cassini. Cassini took him with him to
the observatory, and employed him under him, where he
made a very rapid progress in the science. In 1683, the
academy carried on the great work of the meridian to the
north and south, begun in 1670, and Cassini having the
southern quarter assigned him, took in the assistance of
Chazelles. In 1684, the duke of Montemart engaged
Chazelles to teach him mathematics, and the year after
procured him the preferment of hydrography-professor for
the gallies of Marseilles, where he set up a school for
young pilots designed to serve on board the gailies. In
1686, the gallies made four little campaigns, or rather four
courses, for exercise, during which Chazelles always went
on board, kept his school on the sea, and shewed the
practice of what he taught. He likewise made a great
many geometrical and astronomical observations, which
enabled him to draw a new map of the coast of Provence.
In 1687 and 1688 he made two other sea campaigns, and
drew a great many plans of ports, roads, towns, and forts,
which were so much prized as to be lodged with the
ministers of state. At the beginning of the war which
ended with the peace of Ryswick, Chazelles and some
marine officers fancied the gailies might be so contrived as
to live upon the ocean, and might serve to tow the men of
war when the wind failed, or proved contrary; and also
help to secure the coast of France upon the ocean. He
was sent to the western coasts in July 1689 to prove this
scheme; and in 1690 fifteen gailies, new-built, set sail
from Rochefort, cruised as far as Torbay in England,
and proved serviceable at the descent upon Tinmouth.
Here he performed the functions of an engineer, and
shewed the courage of a soldier. The general officers he
served under declared that when they sent him to take a
view of any post of the enemy, they could rely entirely
upon his intelligence. The gallies, after their expedition,
came to the mouth of the Seine into the basons of Havre
de Grace and Honfleur; but could not winter because it
was necessary to empty these basons several times, to prevent the stagnation and stench of the water. He proposed
to carry them to Rohan; and though all the pilots were
against him, objecting insuperable difficulties, he succeeded in the undertaking* While he was at Rohan he
digested into order the observations which he had made on
the coasts, and drew distinct maps, with a portulan to
them, viz. a large description of every haven, of the
depth, the tides, the dangers and advantages discovered,
&c. which were inserted in the “Neptune Francois,
” published in Neptune François
”
carried on to a second volume, which was also to include
the Mediterranean. Chazelles desired that he might have
a year’s voyage in this sea, for making astronomical observations; and, the request being granted, he passed by
Greece, Egypt, and the other parts of Turkey, with his
quadrant and telescope in his hand. When he was in
Egypt he measured the pyramids, and found that the four
sides of the largest lay precisely against the four quarters
of the world. Now as it is highly probable that this exact
position to east, west, north, and south, was designed
3000 years ago by those that raised this vast structure, it
follows, that, during so long an interval, there lias been
no alteration in the situation of the heavens; or, that the
poles of the earth and the meridians have all along continued the same. He likewise made a report of his voyage
in the Levant, and gave the academy all the satisfaction
they wanted concerning the position of Alexandria: upon
which he was made a member of the academy in 1695.
Chazelles died Jan. 16, 1710, of a malignant fever. He
was a very extraordinary and useful man; and, besides his
great genius and attainments, was also remarkable for his
moral and religious endowments.