twenty-two he was a Professor of Natural Philosophy at the University of Glasgow. When little more than out of his teens, Sir William Thomson became editor of the _Cambridge and Dublin Mathematical Journal_, through which a great impetus was given to the study of pure and applied mechanics; and before the era of the Atlantic Cable he contributed many papers on telegraphy to the Royal Society, in connection with which he made the acquaintance and enjoyed the esteem of such men as Faraday and Brewster. The Natural Philosophy Chair in Glasgow University he has raised to a high rank--perhaps the highest of its kind in the world, and students come from far and near to sit at the feet of this Gamaliel among the physicists of his day and generation." The Bakerian lecture, entitled "The Electro-Dynamic Properties of Metal," was delivered by Sir William Thomson in 1855, and by that and kindred contributions to scientific literature he was rapidly laying the foundation of his great reputation. In 1854 he published a series of investigations, by which he shows that the capacity of the conducting wire for the electric charge depends on the ratio of its diameter to that of the gutta percha covering; and in the face of much opposition he established what is now known as the "law of squares," which asserts that the rate of transmission is inversely as the square of the length of the cable. These results were of much utility in their bearing on the working of submarine cables, and it is not too much to affirm that it was to Sir William Thomson's counsel that the success of the Atlantic Cable is in great part due. His mirror galvanometer was the first instrument that could be applied with anything like satisfactory results to submarine telegraphy. More recently, however, he has invented and patented another instrument, called the "syphon recorder," which was exhibited publicly for the first time at the opening of the British India Submarine Telegraph. The special feature of the "syphon recorder" is a minute capillary syphon, which, while it continually discharges ink against a moving paper, is by means of a delicate electro-magnetic arrangement caused to move from side to side _according to the electric pulses passed through the cable_, and from the record thus obtained of these motions the message is deciphered. From trials lately made on the Falmouth, Gibraltar, and Malta lines, it has been ascertained that 25 words per minute can be registered through a cable 800 miles long. It is also a recommendation to the "syphon recorder" that it can be worked by very low battery power, and therefore tends to the preservation of the cable. Among Sir William's other inventions we may specially mention an electrometer, which has now assumed a very complete form. His divided-ring electrometer admitted of accurate measurements, in skilled hands, of fractions of a Daniell's cell; his portable electrometer admits of readings from 10 or 20 cells upwards; but his new reflecting