The great interest attaching to transit-circle work is this striving after ever greater and greater precision, with the result of bringing out fresh little discordances, which, at first sight, appear purely accidental, but which, under further scrutiny, show themselves to be subject to some law. Then comes the hunt for this new unknown law. Its discovery follows. It explains much, but when it is allowed for, though the observations now come much closer together, little deviations still remain, to form the subject of a fresh inquiry. Astronomy has well been called the exact science, and yet exactitude ever eludes its pursuer. If it be asked, 'What is the use of this ever-increasing refinement of observation?' no better answer can be given than the words of Sir John Herschel in one of his Presidential addresses to the Royal Astronomical Society:-- 'If we ask to what end magnificent establishments are maintained by States and sovereigns, furnished with masterpieces of art, and placed under the direction of men of first-rate talent and high-minded enthusiasm, sought out for those qualities among the foremost in the ranks of science, if we demand, _cui bono?_ for what good a Bradley has toiled, or a Maskelyne or a Piazzi has worn out his venerable age in watching?--the answer is, Not to settle mere speculative points in the doctrine of the universe; not to cater for the pride of man by refined inquiries into the remoter mysteries of nature; not to trace the path of our system through space, or its history through past and future eternities. These, indeed, are noble ends, and which I am far from any thought of depreciating; the mind swells in their contemplation, and attains in their pursuit an expansion and a hardihood which fit it for the boldest enterprise. But the direct practical utility of such labours is fully worthy of their speculative grandeur. The stars are the landmarks of the universe; and, amidst the endless and complicated fluctuations of our system, seem placed by its Creator as guides and records, not merely to elevate our minds by the contemplation of what is vast, but to teach us to direct our actions by reference to what is immutable in His works. It is, indeed, hardly possible to over-appreciate their value in this point of view. Every well-determined star, from the moment its place is registered, becomes to the astronomer, the geographer, the navigator, the surveyor, a point of departure which can never deceive or fail him, the same for ever and in all places; of a delicacy so extreme as to be a test for every instrument yet invented by man, yet equally adapted for the most ordinary purposes; as available for regulating a town clock as for conducting a navy to the Indies; as effective for mapping down the intricacies of