One bright morning Dr. Wollaston came to pay us a visit in Hanover Square, saying, "I have discovered seven dark lines crossing the solar spectrum, which I wish to show you;" then, closing the window-shutters so as to leave only a narrow line of light, he put a small glass prism into my hand, telling me how to hold it. I saw them distinctly. I was among the first, if not the very first, to whom he showed these lines, which were the origin of the most wonderful series of cosmical discoveries, and have proved that many of the substances of our globe are also constituents of the sun, the stars, and even of the nebulae. Dr. Wollaston gave me the little prism, which is doubly valuable, being of glass manufactured at Munich by Fraunhofer, whose table of dark lines has now become the standard of comparison in that marvellous science, the work of many illustrious men, brought to perfection by Bunsen and Kirchhoff. * * * * * Sir William Herschel had discovered that what appeared to be single stars were frequently two stars in such close approximation that it required a very high telescopic power to see them separately, and that in many of these one star was revolving in an orbit round the other. Sir James South established an observatory at Campden Hill, near Kensington, where he and Sir John Herschel united in observing the double stars and binary systems with the view of affording further data for improving our knowledge of their movements. In each two observations are requisite, namely, the distance between the two stars, and the angle of position, that is, the angle which the meridian, or a parallel to the equator makes with the lines joining the two stars. These observations were made by adjusting a micrometer to a very powerful telescope, and were data sufficient for the determination of the orbit of the revolving star, should it be a binary system. I have given an account of this in the "Connexion of the Physical Sciences," so I shall only mention here that in one or two of the binary systems the revolving star has been seen to make more than one revolution, and that the periodical times and the elliptical elements of a great many other orbits have been calculated, though they are more than 200,000 times farther from the sun than we are. After Sir John Herschel was married, we paid him a visit at Slough; fortunately, the sky was clear, and Sir John had the kindness to show me many nebulae and clusters of stars which I had never seen to such advantage as in his 20 ft. telescope. I shall never forget the glorious appearance of Jupiter as he entered the field of that instrument.