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Art. II.— Observations on Changeable Stars, and Stars of 
different Colours. 
T HERE is no branch of astronomy more pregnant with inte- 
rest than that of stars which shine with a variable and periodical 
lustre. Our countryman Mr Pigott was the first astronomer 
who devoted his attention to this class of phenomena. He es- 
tablished the existence of fifteen stars which shine with a va- 
riable light, and gave a catalogue of observations on thirty-se- 
ven stars which he suspected to have the same property. Sir 
William Herschel made many valuable observations on the same 
subject, the results of which are to be found even in our popu- 
lar treatises on astronomy. 
Three German astronomers, M. Struve of Dorpat in Livonia, 
and MM. Harding and Westphal of Gottingen have recently 
been engaged in the observation of periodical stars. M. Struve 
has begun to publish his results in the Collection of his Astro- 
mical Observations for 1818 and 1819, which appeared at Dor- 
pat in 182L He there describes stars of all colours*, white, 
yellow, blue, and red, with all their different shades. He has 
determined also the constant of aberration for several of these 
stars, of all magnitudes and colours, and, from finding the same 
result, he concludes that they all project their light with the 
same velocity. 
M. Harding has discovered several new variable stars ; and 
M. Westphal has published his observations on the same sub- 
ject in Lindenau and Bohnenberger’s Astronomical Journal. 
Unfortunately for science, a valuable memoir on changeable 
stars, which he had composed in 1817 for the above work, was 
lost at the printing-office. 
The following catalogue of twenty-eight changeable stars has 
been recently published by Baron de Zach in his Correspon- 
dence Astronomique , vol. viii. p. 99- 
* His terms are, alba, obscura, obscurissima, livida, pallida, flava, subflava, 
eoerulea, subcoerulea, rubra, rubicunda, &c. 
