The "most expensive sea-atlas ever published in Amsterdam in the seventeenth century" (Koeman)

This monumental atlas is made up of three works: 'Le neptune François'; 'Cartes marines a l'usage des armées du Roy de la Grande Bretagne'; and 'Suite du neptune François'. The first two parts were first published by Mortier in 1693, the third was issued by him in 1700.

The first part contains all 12 plates of naval ensigns and 31 charts (two more than called for by Koeman), which detail European waters from the Baltic to Portuguese coast. They are not only more lavish than any of those produced previously, but also are drawn upon Mercator's Projection – only the second sea atlas to do so (for the first, see item 16). The two extra charts are Mortier's world map of 1693, and a chart of Europe's Atlantic coast.

The second part, 'Cartes marines a l'usage des armées du Roy de la Grande Bretagne', which contains nine charts, constitutes "the most spectacular type of maritime cartography ever produced in seventeenth century Amsterdam" (Koeman). It was prepared for the use of William III who needed accurate information on the Channel coasts for his war plans against Louis XIV of France. In 1694 he sent an expedition to attack several of the ports which are illustrated in the etched vignettes that decorate these charts. What has won their lasting fame, however, is the identity of their author: the artist-engraver Romeijn de Hooghe (1645–1708). Since he undertook all stages of production himself, the charts exhibit a rare harmony of design and execution. The allegorical subjects which characterise his paintings are here transformed into dramatic cartouches. No chart illustrates this better that his monumental chart of the Mediterranean, one of the most beautiful charts ever engraved.

The third part, first issued in 1700 as a supplement to the first, contains 37 charts, of which 20 cover the Africa coast, five Asia, and 11 the Americas. The volume also boasts the table Boussole des Vents, or table of winds, and a suite of 19 naval plates. The charts in the 'Suite' are, for the most part, new productions by Mortier, as opposed to the close-copying of Parisian charts in the first volume, and Mortier used sources such as the 'English Pilot' volumes for the American coasts. The present example also includes a fine impression of the celebrated world chart by Edmond Halley, together with the printed Dutch translation of Halley's explanation which is frequently missing.

Halley's isogonal chart first appeared as a separate publication in 1702, and Pieter Mortier's close copy was probably issued shortly after. Halley's Atlantic voyages, undertaken in the 'Paramore' between 1698 and 1700, have been described as "the first sea journeys undertaken for a purely scientific object". The resulting chart attempted, for the first time, to show the global incidence of isogonal lines enclosing areas in which the magnetic variation from true north was held to be constant. Mortier's version is the first atlas dissemination of the chart, and was also the first to give the chart its westward extension, causing Australia and the Far East to appear on both sides of the sheet.

Another chart of note is the chart of eastern Canada, with a new depiction of the Hudson Bay, based mostly on the work of Alexis Hubert Jaillot (1685) which used the accounts of Louis Jolliet and Fr Louis Hennepin in the upper Mississippi Valley and Great Lakes region. The outline of Hudson Bay is superior to that shown on chart 36 ('Carte particuliere de l'Amerique'), which is based on English mapping of the 1690s. The present chart, closely copied by Mortier, shows accurately the discoveries of Button in 1612 and 1613, and those of Foxe and James in 1631 and 1632. Inland, on the Nelson River, the chart shows that Jaillot, in his map of 1685, had access to knowledge of Lake Winnipeg derived from Indian reports. The lake itself was discovered in 1690 by Henry Kelsey, who also was the first to report of the prairies as a land which "affords nothing but beast and grass".

Finally, the 'Carte Particuliere de Virginie, Maryland, Pennsilvanie, la Nouvelle Jersey' included is also worthy of attention. The chart covers Chesapeake Bay and the Delaware River as far as Philadelphia, laid out in 1682 and based upon John Thornton's chart in the 'English Pilot' (1689). It represents one of the earliest detailed charts of the American coast.

Collation:
— Part I: 'Neptune François': 12 plates of naval ensigns, and 31 charts.
— Part II: 'Cartes marines … du Roy de la Grande Bretagne': nine charts.
— Part III: 'Suite du Neptune François': one wind chart, 19 plates of ships, and 37 charts.

A full collation is available on request.