and the Riddle edition of 1840; Dublin, 1790).

[353] Hendryk van Etten, the _nom de plume_ of Jean Leurechon (1591-1670),
rector of the Jesuit college at Bar, and professor of philosophy and
mathematics. He wrote on astronomy (1619) and horology (1616), and is known
for his _Selecta Propositiones in tota sparsim mathematica pulcherrime
propositae in solemni festo SS. Ignatii et Francesci Xaverii_, 1622. The
book to which De Morgan refers is his _Recreation mathematicque, composee
de plusieurs problemes plaisants et facetieux_, Lyons, 1627, with an
edition at Pont-a-Mousson, 1629. There were English editions published at
London in 1633, 1653, and 1674, and Dutch editions in 1662 and 1672.

I do not understand how De Morgan happened to miss owning the work by
Claude Gaspar Bachet de Meziriac (1581-1638), _Problemes plaisans et
delectables_, which appeared at Lyons in 1612, 8vo, with a second edition
in 1624. There was a fifth edition published at Paris in 1884.

[354] His title page closes with "Paris, Chez Ch. Ant. Jombert.... M DCC
LIV."

This was Charles-Antoine Jombert (1712-1784), a printer and bookseller with
some taste for painting and architecture. He wrote several works and edited
a number of early treatises.

[355] The late Professor Newcomb made the matter plain even to the
non-mathematical mind, when he said that "ten decimal places are sufficient
to give the circumference of the earth to the fraction of an inch, and
thirty decimal places would give the circumference of the whole visible
universe to a quantity imperceptible with the most powerful microscope."

[356] _Antinewtonianismi pars prima, in qua Newtoni de coloribus systema ex
propriis principiis geometrice evertitur, et nova de coloribus theoria
luculentissimis experimentis demonstrantur_.... Naples, 1754; _pars
secunda_, Naples, 1756.

[357] Celestino Cominale (1722-1785) was professor of medicine at the
University of Naples.

[358] The work appeared in the years from 1844 to 1849.

[359] There was a Vienna edition in 1758, 4to, and another in 1759, 4to.
This edition is described on the title page as _Editio Veneta prima ipso
auctore praesente, et corrigente_.

[360] The first edition was entitled _De solis ac lunae defectibus libri
V. P. Rogerii Josephi Boscovich ... cum ejusdem auctoris adnotationibus_,
London, 1760. It also appeared in Venice in 1761, and in French translation
by the Abbe de Baruel in 1779, and was a work of considerab