The finding of the longitude, which is still a desideratum in the art, had even early en gaged the attention of writers, for we find that Pedro Nunez, or Nonius, published a treatise on this subject in 1537 in the Portuguese lan guage, which was afterwards printed at Basil in Latin, under the title of 'De Arte et Ratione Navigandi.' In this work the problem of de termining the latitude from two observations of the sun's altitude and the intermediate azimuth is resolved. In 1557, Bourne pub lished his 'Regiment for the Sea,' intended as a supplement to Cortes, and in 1581 Michael Coignet, a native of Antwerp, published his 'Instruction Nouvelle des Points plus excel Lens et necessaires touchant I' Art de Naviger; intended as an improvement upon Medina.. The discovery of the dipping-needle was ex plained by Robert Norman in his New At tractive,' a pamphlet, to which is commonly subjoined William Burrough's 'Discourse of the Variation of the Compass.' In 1594, Captain John Davis published a small treatise, entitled the 'Seaman's Secrets,' which was much esteemed at that time.
As the errors of the plane chart had been much complained of by those who were con versant with the subject, Gerard Mercator was led to construct a universal map, for the purpose of obviating those objections, the use of which was afterwards fully illustrated by Mr. Edward Wright, of Cambridge, who, in
his Correction of certain Errors in Naviga tion,' printed in 1599, showed the true method of dividing the meridian from Cambridge, as also the manner of constructing the table, and its uses in navigation. The method of ap proximation by what is called the middle lati tude, is mentioned by Gunter in his works, printed in 1623, but was not brought into ge neral use until some time after. The tion of logarithms to navigation was also made by this author in a variety of ways ; but Thomas Addison, in his Arithmetical Navi gation,' is said to have been the first to apply logarithmic tables to the cases of sailing. From this time several writers in England and elsewhere contributed to the improve ment of the science, as Gellibrand, in a 'Dis course Mathematical on the Variation of the Needle;' Norwood, in his Seaman's Frac tice ; John Baptist Riccioli, at Bologna, in 1661 ; Father Millet Dechals, in 1674 and 1677 ; M. Bongier, in 1698 ; William Jones, in a New Compendium of the whole Art of Navigation; Peter Bouque, in his ' Nouveau Traite de Navigation ; and Dr. Robertson's Elements of to which was add ed a valuable preface by Dr. James Wil son.