168 H. M. Parkhurst on a Star-Mapper. 
the middle of their motion; but moving the arm K, either 
this modification, I believe this construction to be absolutely 
free from theoretic inaccuracy ; and I believe it to be the only 
apparatus yet devised to record with theoretic accuracy, by 
mechanical means, the right ascension and declination at the 
same instant, or in other words, to make a chart of the stars 
observed, the errors of which shall be entirely errors of obser- 
vation and inaccuracy in the mechanical construction of the 
ere it is accessible. Then pressing down 
the knob, I properly turn the manual on its axis, with my 
ing bar upon the star-point, At that instant I tap on the 
manual and the star is mapped. I then select another star and 
map it in the same way; and so on, ata rate varying from 
2 ae ee 
