xxx ix 



now an increasing deafness excluded him to a great extent from the plea- 

 sures of social intercourse. This infirmity, which was almost the only- 

 sign of his great age, he bore with patience and resignation. He had sur- 

 vived all the friends of his youth and most of those of his manhood ; but 

 he was\appyin the possession of mental resources, which enabled him to 

 indulge, even to his last day, the habits of constant industry which he had 

 acquired when a boy.. As with advancing age he became less inclined for, 

 and at last less capable of, deep study or long-sustained thought, his em- 

 ployments partook more of the nature of pastimes ; but both in his selec- 

 tion and pursuit of these there might still be traced the scientific turn of 

 thought and philosophical love of method which had characterized the 

 main achievements of his life. The engines he had forged to store his 

 mind were now employed to entertain his leisure. One example of this 

 was very remarkable. At an early period (May 1811) he had attended a 

 course of lectures by the celebrated Feinaigle, of whose system of Mnemo- 

 nics he made constant use throughout life. This system comprises two 

 main devices for a memoria technica. The one is designed to record chro- 

 nological facts, or indeed any facts connected with the ordinary succession 

 of numbers, the other to impress separate figures upon the memory. The 

 first object is accomplished by a methodical arrangement in well-known 

 portions of space, such as the sides of a room ; the second by means of 

 words which can be easily remembered, and of which the letters are made 

 to represent figures under a conventional rule of interpretation. Of both 

 these sources Dr. Roget had availed himself largely. He had applied the 

 former to a great variety of subjects. For him familiar places had thus 

 an additional interest. The houses he had lived in, and those of friends 

 whom he had visited, the old rooms of the Royal Society at Somerset 

 House, and of various Institutions which he frequented, were pictured to 

 his mind's eye as peopled with an infinitude of facts, and teeming with 

 varied information. The chronicle of universal history, the measurement 

 of earth and sky, the epochs of his life and of those of his contemporaries, 

 the sources of his income, the categories of his ' Thesaurus,' the general 

 arrangement of human knowledge, were all recorded in this manner on the 

 tablets of his memory. Of the second device, he had also made extensive 

 application. Logarithms, approximations to surds, and various ratios in 

 common use in computation were set by him to doggrel phrases, which it 

 was an amusement to repeat to himself as he walked ; and he would some- 

 times astonish his acquaintance by accurately stating the value of ir to forty 

 or fifty places of decimals. 



He was always fond of mechanical contrivances, and at one period spent 

 much time and labour in attempts to construct a calculating machine. This 

 design he abandoned on seeing the beautiful engine of Professor Scheutz, 

 of which he at once admitted the superiority. He also made some progress 

 tqwards the invention of a delicate balance, in which, to lessen the effect 

 of friction, the fulcrum was to be within a small barrel floating on water. 



VOL. XVIII. f 



