The genius of Carl Friedrich Gauss (1777-1855) and the velty of his work (published in Latin, German, and occasionally French) in areas as diverse as number theory, probability and astromy were already widely ackwledged during his lifetime. But it took ather three generations of mathematicians to reveal the true extent of his output as they studied Gauss' extensive unpublished papers and his volumius correspondence. This posthumous twelve-volume collection of Gauss' complete works, published between 1863 and 1933, marks the culmination of their efforts and provides a fascinating account of one of the great scientific minds of the nineteenth century. Volume 12, which appeared in 1929, contains a great variety of posthumous tes and fragments, scientific correspondence and even proposals for problems to be set at scientific competitions. The volume also includes a reproduction of Gauss' 1840 atlas of geomagnetism.