378 Dr. Herschel's Account of the Changes that have happened 
to point out the uncertainties in which the investigation of the 
periodical time of the small star about e Bootis must long remain 
involved. 
f Herculis. 
My observations of this star furnish us with a phenomenon 
which is new in astronomy; it is, the occultation of one star by 
another. This epoch, whatever be the cause of it, will be equally 
remarkable, whether owing to solar parallax, proper motion, or 
motion in an orbit whose plane is nearly coincident with the 
visual ray. My first view of this star, as being double, was 
July 18, 1782. With 460, the stars were then \ diameter of the 
small star asunder. The large star is of a beautiful bluish white; 
and the small one ash-coloured. 
July 21, of the same year, I measured the angle of position, 
20 0 42' north following. With the standard power, the distance 
of the stars remained as before. With 987, they were one full 
diameter of the small one asunder. 
In the year 1795, I found it difficult to perceive the small 
star; however, in October of the same year, I saw it plainly 
double, with 460 ; and its position was north following. 
Other business prevented my attending to this star till the 
year 1802, when I could no longer perceive the small star. 
Sometimes, however, I suspected it to be still partly visible; and, 
in September of the same year, with 460, the night being very 
clear, the apparent disk of £ Herculis seemed to be a little 
lengthened one way. With the 10-feet telescope, and a power 
of 600, I saw the two stars of vj Coronas very distinctly ; and, 
having in this manner proved the instrument to act well, I di- 
rected it to f Herculis, and found it to have the appearance of a 
