A few instances will suffice to show the kind of observations made by this notable firm of Pound and Bradley. They observed the positions of the fixed stars and nebulæ: these being generally the results required by Halley and Newton. They also observed the places of the planets among the stars, and especially the planet Mars, and determined its distance from the Earth by the method of parallax, thus anticipating the modern standard method of finding the Sun's distance; and though with their imperfect instruments they did not obtain a greater accuracy than 1 in 10, still this was a great advance on what had been done before, and excited the wonder and admiration of Halley. They also paid some attention to double stars, and did a great deal of work on Jupiter's satellites. We might profitably linger over the records of these early years, which are full of interest, but we must press on to the time of the great discoveries, and we will dismiss them with brief illustrations of three points: Bradley's assiduity, his skill in calculation, and his wonderful skill in the management of instruments. Of his assiduity an example is afforded by his calculations of the orbits of two comets which are still extant. One of them fills thirty-two pages of foolscap, and the other sixty; and it must be remembered that the calculations themselves were quite novel at that time. Of his _skill_ in calculation, apart from his assiduity, we have a proof in a paper communicated to the Royal Society rather later (1726), where he determines the longitudes of Lisbon and New York from the eclipses of Jupiter's satellites, using observations which were not simultaneous, and had therefore to be corrected by an ingenious process which Bradley devised expressly for this purpose. And finally, his skill in the management of instruments is shown by his measuring the diameter of the planet Venus with a telescope actually 212-1/4 feet in length. It is difficult for us to realise in these days what this means; even the longest telescope of modern times does not exceed 100 feet in length, and it is mounted so conveniently with all the resources of modern engineering, in the shape of rising floors, &c., that the management of it is no more difficult than that of a 10-foot telescope. But Bradley had no engineering appliances beyond a pole to hold up one end of the telescope and his own clever fingers to work the other; and he managed to point the unwieldy weapon accurately to the planet, and measure the diameter with an exactness which would do credit to modern times. A few words of explanation may be given why such long telescopes were used at all. The reason lay in the difficulty of getting rid of coloured images, due to the composite character of white light. Whenever we use a _single_ lens to form an image, coloured fringes appear. Nowadays we know that by making two lenses of different kinds of glass and putting them together, we can