179 



vations, which, beginning about the time that Sir John left off (1 838), 

 have been continued up to the present year. All the conclusions, 

 indeed, ventured on by formoi* authorities have turned out erroneous ; 

 but the close approximation to the truth now obtained exhibits far 

 more interesting features than were ever expected. At the epochs 

 of Lacaillo and Maskelyne, the distance was on the decrease, 

 instead of the increase ; and the stars were seen in almost exactly the 

 same relative position by the latter observer in 1761, as by Sir J. 

 Herschol in 1030 ; and in the interval they had, instead of merely 

 gaining the aphastre without sensible change of angle of position, really 

 made a whole revolution, and altered that angle by 360°. The period 

 is about 77 years ; the mass three-fourths of the solar ; the greatest 

 distance 22"-5, the least distance 0"*5 ; and the periastre takes place 

 in 185 1-5, when, on account of the excessive excentricity of the orbit, 

 the change of angle of position will be actually 2° 40' per day. 



That will, therefore, be a most crucial period for testing the theory 

 by observations of the facts ; and aflPords the very best and strongest 

 instance for it of all the double stars yet discovered ; in addition to 

 which, the accurate determination of the parallax of the star by 

 Professor Henderson gives it a crowning importance. 



2. On the Colouring Matter of the Morinda citrifolia. By 

 Dr Thomas Anderson. 



The substance examined by the author was imported into Glas- 

 gow from Bombay, under the name of sooranjee, as a substitute for 

 madder, but had been found useless by the dyers. No information 

 could be obtained regarding its botanical origin in this country, but 

 the importers having written to their correspondents received a quan- 

 tity of seeds, labelled, Seeds of the Sooranjee plant, Morinda citrifolia. 

 These seeds did not germinate, but agreed in their characters with 

 those oi M. citrifolia ; and, for reasons stated at length in the paper, 

 are considered by Dr Balfour to belong to that plant. 



The colouring matter to which the author applies the name of 

 morindine, was extracted from the bark of the root by boiling alco- 

 hol, and purified by successive crystallizations, and finally by solu- 

 tion in boiling spirit, acidulated with hydrochloric acid, which was 

 found necessary for the separation of the last traces of ash. It then 

 was in the form of minute acicular crystals of a fine yellow colour- 



