CELESTIAL MEASURINGS AND WEIGHINGS. 213 



optician of New York, turning on Sirius a fine telescope 

 of his own construction, noticed extremely near to it a 

 minute star which had eluded all former observation. 

 This may be the body in question. There is even some 

 reason to suppose it is. Its apparent situation is stated 

 to be at least not such as to be incompatible with such 

 a connexion. Its real existence has been verified, and its 

 apparent distance from Sirius measured, and found to be 

 about seven seconds ; corresponding (if seen unfore- 

 shortened) to about forty-seven times the distance of 

 the sun from the earth. 



(40.) Another beautiful specimen of these binary side- 

 real systems is presented by the star No. 70 in Flam- 

 steed's list of those in the constellation Ophiuchus, and 

 therefore cited as 70 Ophiuchi. The ellipse described 

 by the stars of this pair (the one a star of the fourth, the 

 other of the sixth, magnitude) has been determined with 

 much care and every probability of considerable pre- 

 cision. The period of their mutual circulation may be 

 stated at about ninety-six years, and the semiaxis of their 

 mutual ellipse in angular measure at 4"'8. Of this ele- 

 gant couple the parallax has been ascertained by M. 

 Kriiger, from observations made in 1858 and 1859, at 

 o"-i6. And from these data he concludes in the very 

 same way : First, their distance from our own system 

 (1,272,000 semi-diameters of the earth's orbit) ; sec- 

 ondly, the mean distance of the stars from each other 

 (30^ such semi-diameters, so that here also their relative 

 orbit is nearly equal to that of Neptune) ; and, thirdly, 

 the total mass (equivalent to 3^ times that of the sun). 



