Page:The New International Encyclopædia 1st ed. v. 14.djvu/354

NAVIGATION. 310 NAVIGATION. Aleiiitcrrancan and on the Atlantic coast of Uaul. for the protection of connnene. The barbarian nations of the North developed the art of navi-xation in their o«ii way. The Sa.Nons. .fntes. and Norsemen began to roam the ocean in every direction; in small vessels they trusted more" to the winds than to oars, and, sailiiifr singly, gradually ac<iuircd that har- dihood and daring which ultimately rendered them masters of the sea. The Norsemen extended their voyages to Iceland, t^reenland, and New- foundland, while they first ravaged and then colonized the coasts of Britain, France, and Sicilv. In" the Middle Ages the Venetians, the Gen- oese, and the Pisans became the carriers of the Mediterranean Sea. Their merchants traded to the farthest Indies, and their markets became the exchanges for the produce of the world. Their constant rivalries gave occasion for the growth of naval tactics. So rich a commerce tempted piracy, and the Mohammedan corsairs spread over the Mediterranean, and, passing through the Straits of (Jibraltar, ravaged the .Atlantic coast. The mariner's compass (q.v.) came into quite general >ise in the thirteenth century, and rendered the seaman independent of the sun and stars, so far as simple steering was concerned. The variation of the compass from true north seems to have been observed as early as 1269, but it was not until the voyages of Columbus that much attention was paid to it. It was not until the thirteenth century that the employment of (he mariner's compass brought about the <levcln[imcnt of practicMl nautical charts. ( Kor ancient cartography, see (!EO(iKAP]iY and Mai'. ) These first appeared in Italy: they were constricted by the aid of the compass and took the name of compass charts. The oldest of them is the .so-called Pisan chart, which belongs probably to the middle of the thirteenth cintury. and it covers th(^ whole of the Mediterranean. The earliest chart of which the exact <Iate is known appears to be that of P. Visconte (1311). These charts are all plane, and together with other early ones are chielly of the Mediter- ranean : but some of those appearing in the fourteenth century show the Azores, the Canaries, and the coast of Africa as far as Cape Hojador. The translation and dissemination of Ptolemy's works in the lifteenth century caused a great improvement in maps i d charts, and the subse- quent labors of Copernicus and MtMcator brought them to a very satisfactory state, considering the lack of geographical information. Mcrcator (l.)12-!)4) engraved an extensive atlas. Kdward Wright, who jnd>lished in l.i!l'.> a work entitled Certain ICnors In .Yrriiffn/ioH Detcrtril and Cor- rected, gives a complete exposition of the proper method of constructing a Mereator's projection, together with other information of value. In what is known as Mereator's projection, meridians are straight lines parallel to each other, and are crossed by the parallels of latitude at right angles. In order to preserve the proportion that exists in (he curved surface of the eardi and render the (rack of the ship (loxodromie curve) a straight line on the chart, the meridians are expanded or increased in length. The augmented latitu<les are computed and published in a taVile of 'meridional parts' by means of which the parallels of latitude are placed. In Mcrcator charts of great extent the areas of portions dilVcriiig much in latitude are greatly out of pio]Mirtion, but contiguous areas dill'ering little in latitude compare fairly well. The rude character of the early instruments used in navigation prevented close determination of a ship's position at sea. Watches were un- known until about loSO, when Gemma Frisius im- mediately recognized the possibility of using them for the purpose of ascertaining the dilTcr- ence of longitude between two |)laces. These early timepieces were very defective, however, and it was not until 17IJ.5 that Harrison was awarded 110,000 by the Hritish (lovermiient for his clironometer, a second £10,000 whidi he re- ceived being paid in 1773 after further trials of his invention. The date of the first attempts at determining latitude by measuring the altitude of lieavenly bodies (at first, the fixed stars) is unknown, but Columlius is said to have had a eross-stalT (see Sexta.nt) for this purpose. Somewhat later the astrolabe was devised. In 1.504 the celebrated navigator Uavies published in his pamphlet entitled The Scunian's Secrets a mollifica- tion of the cross-statr. In using this instrument the observer stood with his back to the sun look- ing at the horizon through a sight at the end of the statT. while the shadow of a movable projec- tion fell on the sight box. In 1720 Pierre Bougeur devi.sed an improved form of Davies's instru- ment. This was followed almost immeiliately by the invention of the quadrant by Iladley in Eng- land, who described his iustnimcnt in a |)aper to the Koyal Society in .May 1731, and by Thomas Godfrey of Philadelphia, who made an instru- ment as earlv as 1730 that was used at sea in August, 1731! The earliest work devoted specially to navi- gation was that of Pedro de Medina, i)iib- lished at Valladolid in 1545. In 1530 Gemma Frisius wrote upon astnmomy, cosmogony, and the use of globes. In 1537 Pedro Nunez ( Nonius | , cosmographer to the King of Portugal, published a work on astronomy, charts, and some parts of navigation. In 155U Martin Cortes jiuhlished at Seville The Art of yarigation. Davies. in The Kcaman's Secrets, defines three kinds of sailings — horizontal, paradoxical, and great- circle, '^rhe paradoxical embraced latitude, longitude, and distance, and combined what are now called traverse and Mereator's sailings. He also gave a clear description of great-circle .sail- ing and the proper method of aeeomiilishing it. .moiig the developments in navigatiiui in the nineteenth century were the patent log. the Thomson s<iiinding machine, the Thcuusnn com- pass, the Kitchic liquid compass, compensation of the deviations of the compass, and the great- circle sailing chart. Almost all the old ap- pliances were tniich improved, and steam pro|>ul- sion has greatly simidificd navigating ])roblcms. Charts (q.v.) are uinlcrgoing constant correction and are. considering all things, wonderfully ac- curate, but much can yet be done and is being done. The most serious enemies of the naviga- tor of the present day are fogs and irregular cur- rents, MODKRN AUT OK XAVIOATION, In the merchant service vessels are taken in and out of port by a pilot. When the vessel is ready (o leave port, the pilot (or captain in the Inited States Navy) takes charge. Men are