10 It must be pointed out that the Palermo circle did not perform any better than, say, Bird’s quadrant at Greenwich. Piazzi, after working with it, estimated between 1 and 3 arc-seconds the possible systematic error. However this does not lessen the relevance of the instrument and it must be credited to Piazzi to have clearly foreseen that the circular instruments were the instruments of the future: "After what I have been arguing none can possibly doubt the superior advantages of an entire circle over the most perfect quadrant, of equable radius. The hinderance lays essentially in the tooling, but if astronomers will set their minds to use such an instrument, and will gode the tool artists, in a short time the construction of such instruments shall became facile and plain... A circle of six foot radius in the hands of an effective observer will yield the position of the main stars with such an accuracy that only an uncertainty of a fraction of an arc-second would be left. This epoch is perhaps not far in the future and when it will arrive it will beautifully lighten the 18th century for the ages to come" [G. Piazzi, Della Specola Astronomica de’ Regj Studj di Palermo, Palermo 1792, p. 46].