Gauss remained mentally active into his old age, even while suffering from gout and general unhappiness. His last observation was the Solar eclipse of July 28, 1851. At the age of 62, he began to teach himself Russian, presumably to understand the writings of Lobachevsky on non-Euclidean geometry. On 23 February 1855, Gauss died of a heart attack in Göttingen; he is interred in the Albani Cemetery there. Heinrich Ewald, Gauss' son-in-law, and Wolfgang Sartorius von Waltershausen, Gauss' close friend and biographer, gave eulogies at his funeral.
