It was therefore thought at the time that, there being no disturbance from refraction, the disturbance from precession being accurately known, and there being nothing else to disturb the position but "parallax" (the apparent shift due to the earth's motion which it was desirable to find), this star ought to be a specially favourable object for the determination of parallax. Indeed it had been announced many years before by Hooke that its parallax had been found; but his observations were not altogether satisfactory, and it was with a view of either confirming them or seeing what was wrong with them that Molyneux and Bradley started their search. They set up a much more delicate piece of apparatus than Hooke had employed. It was a telescope 24 feet long pointed upwards to the star, and firmly attached to a large stack of brick chimneys within the house. The telescope was not absolutely fixed, for the lower end could be moved by a screw so as to make it point accurately to the star, and a plumb-line showed how far it was from the vertical when so pointing. Hence if the star changed its position, however slightly, the reading of this screw would show the change. Now, before setting out on the observations, the observers knew what to expect if the star had a real parallax; that is to say, they knew that the star would seem to be farthest south in December, farthest north in June, and at intermediate positions in March and September; though they did not know _how much_ farther south it would appear in December than in June--this was exactly the point to be decided. [Illustration: FIG. 2.] [Sidenote: Unexpected results.]