D.S.B. 2: 97-102; Bibliotheca chemico-mathematica, 3rd suppl., no. 945; Houzeau & Lancaster 9069. The German astronomer and mathematician Friedrich Wilhelm Bessel (1784-1846) made the first measurement of a star’s distance by parallax (1838) and calculated the existence of the companion star to Sirius (1844). The present work collects his popular scientific lectures, edited after Bessel’s death by H. C. Schumacher.