observed with the Great Achromatic of Fraunhqfer. 87 



observations of the nebula of Orion. It was only on the 11th 

 November 1826 that I discovered it, although I had examined 

 this nebula several times during two years with Fraunhofer's 

 telescope. Besides, this star appears now to be too brilliant 

 to have escaped the penetration of the great Herschel and 

 Schroeter, as well as the researches of Mr Herschel Junior, 

 who is specially occupied with the nebula of Orion. 



Our telescope has made us only suspect the doubleness of 

 some stars, unfavourable states of the atmosphere frequently 

 not allowing us to make use of the highest magnifying powers. 

 Thus in the new catalogue the bright star Atlas in the 

 Pleiades is indicated as wedge-shaped. A later observation 

 made during the most favourable weather, and with the high- 

 est magnifying powers, has enabled us to discover clearly at the 

 side of this star a companion of the eighth magnitude, which is 

 at the distance of three quarters of a second. But it is very 

 certain that an instrument still more perfect would show many 

 more double stars than the great telescope of Fraunhofer itself 

 can distinguish to be such. 



Our catalogue contains fifty-two triple stars, in each of 

 which the stars are less than thirty-two seconds from one ano- 

 ther. Among these stars there are several, such as No. 11. 

 of the Unicorn, g Cancri, and g Librae (triple stars already re- 

 cognized by Herschel,) where the three stars belong to the 

 bright stars, which proves that they are physically triple stars 

 of ternary systems. These systems, as well as those of qua- 

 druple and quintuple stars, which are not uncommon in the 

 Heavens, while they give a little more extension to the scale of 

 the mutual distances of the stars which compose them, serve 

 as a gradual transition between these double stars and clus- 

 ters of stars. In the case of the triple star g Cancri, the rota- 

 tory motion of the two little stars relative to the principal one 

 is already proved by observation. The star 4» Cassiopeia? fur- 

 nishes us with the example of two little stars very near each 

 other, situated near to a third of greater brightness. If there 

 is here a real connection, so that the star be physically tri- 

 ple, the two little stars ought to turn first round their centre 

 of gravity, and this centre round the bright star. I have al- 

 ready seen this phenomenon three times. The case where two 



