COMETS. 125 



duction, not only many a toilsome and thankless 

 hour was spared, but workers were multiplied 

 and encouraged in the pursuit of labours more 

 useful than attractive." 



Towards the end of 1781 he returned to 

 Bremen, settled as a medical doctor, and con- 

 tinued in practice for about forty -one years. 

 But although he had adopted perhaps the most 

 toilsome profession, his love of science prevailed, 

 and night after night he explored the heavens 

 with untiring zeal. He never slept more than 

 four hours, and the upper part of his house in 

 the Sandgasse, in Bremen, was fitted up with 

 astronomical instruments. The largest telescope 

 which he possessed was a refractor 3f inches 

 in aperture. He remained in active practice 

 till 1823, when he retired, and was enabled 

 to devote more attention to his beloved science. 

 He died on March 2, 1840, at the advanced age 

 of eighty-one. 



Miss Clerke says of Olbers, " Night after 

 night, during half a century and upwards, he 

 discovered, calculated, or observed the cometary 

 visitants of northern skies." He was the dis- 

 coverer of the comet of 1815, known as Gibers' 

 comet. It moves round the Sun in a period 

 of over seventy years, and returned to perihelion 

 in 1887, forty-seven years after the death of its 



