MERCATOR

The Man Who Mapped the Planet

By Nicholas Crane

Henry Holt. 348 pp. $26

MEASURING AMERICA

How an Untamed Wilderness Shaped

The United States and Fulfilled

The Promise of Democracy

By Andro Linklater

Walker. 310 pp. $26

No mapmaker is better known than Gerard Mercator. His ingenious map projection guided generations of navigators, and his famous atlas demonstrated the value of a scholarly compiler-publisher committed to accuracy and editorial consistency. Nicholas Crane brings the great cartographer to life in an engaging biography carefully constructed by integrating Mercator's known accomplishments with key social, military, political and meteorological events of 16th-century Europe.

Born in 1512 to poor parents in Flanders, Gerard Kremer was gifted and lucky. His uncle Gisbert Kremer, a priest, supervised his early education, and at age 7 Gerard could read, write and speak Latin. When the boy was 15, Gisbert arranged to have him enrolled as a scholarship student at a religious boarding school that specialized in penmanship and theology. Before graduating, Gerard changed his surname to Mercator, the Latin equivalent of Kremer, which means merchant in German.

At 18, he entered the university at Louvain, where he studied grammar and philosophy. After graduating, he studied geography and instrument-making in Antwerp. Returning to Louvain, he worked as an apprentice engraver and persuaded the brilliant physician-scientist Gemma Frisius to tutor him in mathematics and astronomy. In 1536, Mercator engraved the lettering for Frisius's terrestrial globe and learned the art of globe-making. A year later they collaborated on a celestial globe, and Frisius acknowledged Mercator as a co-author.

In 1537, Mercator engraved and published his first map, a detailed portrait of Palestine. The following year, he produced his first world map, and in 1541 he introduced his own terrestrial globe, on which spiraling rhumb lines marked courses of constant direction. Three decades later, he would straighten out these spirals on the famous world map that revolutionized navigation.

Mercator lived in turbulent times. Armies fought religious wars and sacked rebellious towns. Crops failed, and epidemics kept the population in check. Explorers made existing maps obsolete overnight. Printing encouraged scholarship and dissent, and heresy was a capital crime. In 1544, religious zealots imprisoned Mercator for alleged Lutheran sympathies but released him seven months later after friends, local officials and his priest interceded. In 1552, weary of religious strife in Flanders, Mercator moved his family to Duisburg, in Germany, to begin a second life at age 40. Continuing to fill orders for his maps and globes, he initiated new projects, including a 15-sheet wall-size map of Europe, a map of Britain based on secret surveys smuggled out of the country by an anonymous clerical collaborator, a massive Chronologia that combined astronomical tables with a carefully researched chronological list of biblical, cultural, political and scientific events from Genesis onward, and a definitive edition of Ptolemy's Geography.

Accuracy was paramount. His 1569 world map, printed in 18 separate sheets that yielded a wall map four feet tall and nearly seven feet wide, offered abundant room for intricate details. Denied the convenience of logarithms and calculus, which had not been invented, Mercator developed its rectilinear grid of meridians and parallels by transferring rhumb lines from a globe. Uncertain of the location of the Earth's north magnetic pole, he included two of them. He traded information with other map publishers, including his friend Abraham Ortelius, who pioneered the modern world atlas in 1570 with his Theatrum Orbis Terrarum. Unlike Ortelius, Mercator enjoyed large, involved projects. He devoted more than three decades to his famous Atlas (which he named after the Titan of Roman mythology), issued in three parts starting in 1585 and completed by his son and grandsons in 1595, a year after his death. Ortelius could claim priority, but Mercator's more comprehensive Atlas gave the new genre its name.

Andro Linklater's Measuring America is another study in cartography, examining the evolution of the square-grid survey system and its impact on the Midwestern landscape. Linklater presents this story as a struggle between decimal-based measurements favored by scientific rationalists and traditional English measurements based on multiples of two or four; it is also a fascinating tale of stubbornness, greed and missed opportunities.

The surveyor's chain devised by Edmund Gunter around 1620 left a lasting imprint on roads and boundaries. With a hundred links extending 66 feet, it established the width of public rights of way (typically one and a half or two chains wide) as well as the length of city blocks (often a multiple of 66 feet). As a bridge between decimal and "four-based" measurements such as inches and feet, Gunter's chain permeates our treatment of length and area: 80 chains make a mile, 10 chains constitute a furlong, and a strip of land a chain wide by a furlong in length is precisely an acre.

Thomas Jefferson, the young Virginia lawyer who emerged as one of the new republic's most influential thinkers, favored decimal measurement based on the geographical mile, defined as one minute of arc along a meridian -- approximately 6,086.4 English feet. As chairman of a congressional committee appointed in 1784 to develop a strategy for surveying and selling off the public lands west of the Appalachians, Jefferson proposed a grid of squares called hundreds. As originally drafted, each hundred was 10 geographical miles on a side and bounded "by lines to be run and marked due north and south, and others crossing these at right angles. . . . these hundreds shall be subdivided into lots one mile square each, or 850 acres and four tenths of an acre, by marked lines."

Before Jefferson's plan could become law, he left for France as U.S. ambassador. When Congress passed the Land Ordinance of 1785, only his grid survived. Instead of decimal units, the new law established townships six English miles on a side and subdivided into 36 square-mile sections easily surveyed with Gunter's chain.

Imposing a rectangular grid on the land was more difficult than plotting lines on a map. In their haste to establish section lines on the Military Reserve in western Ohio, surveyors ignored magnetic declination -- compass needles rarely point directly north -- and laid out a grid four degrees off true north. Failure to compensate for the convergence of meridians led to wide variation in the area of sections: intended as 640-acre squares, some sections in northern reaches of the Reserve were smaller than 600 acres while some in the south exceeded 700 acres.

Jared Mansfield, appointed surveyor-general in 1803, introduced much-needed reform. Sections in Indiana and Illinois are markedly more uniform because he compensated for converging meridians by periodically offsetting north-south boundaries. These offsets are apparent where older north-south roads suddenly jog 50 or 60 yards east or west along a correction line, resulting in hazardous highways -- an unintended consequence of surveyors' diligence.

Linklater examines effects as well as methods. By encouraging rapid settlement and land speculation, expedited surveys prompted the brutal removal of indigenous people. Human impacts are apparent on a lesser scale: Field patterns that ignore natural drainage contribute to erosion, and farmhouses centered on 160-acre, quarter-section lots add to rural isolation. As the rectangular land survey demonstrates, maps don't just describe landscapes; they help mold them. *

Mark Monmonier, the author of "Spying with Maps," teaches cartography at Syracuse University's Maxwell School of Citizenship and Public Affairs.

Gerard Mercator