DESCRIPTIONS OF LECTURES. 99 



a portion of the year. His courses embraced a systematic 1838. 

 view of the whole field of Pure Mathematics, from the 

 first book of Euclid and Elementary Arithmetic up to the 

 Calculus of Variations. From two to three years were 

 ordinarily spent by Mathematical students in attendance 

 on his lectures. De Morgan was far from thinking the 

 duties of his chair adequately performed by lecturing only. 

 At the close of every lecture in each course he gave out a 

 number of problems and examples illustrative of the sub- 

 ject which was then engaging the attention of the class. 

 His students were expected to bring these to him worked 

 out. He then looked them over, and returned them 

 revised before the next lecture. Each example, if rightly 

 done, was carefully marked with a tick, or if a mere inac- 

 curacy occurred in the working it was crossed out, and the 

 proper correction inserted. If, however, a mistake of 

 principle was committed, the words ' show me ' appeared 

 on the exercise. The student so summoned was expected 

 to present himself on the platform at the close of the 

 lecture, when De Morgan would carefully go over the point 

 with him privately, and endeavour to clear up whatever 

 difficulty he experienced. The amount of labour thus 

 involved was very considerable, as the number of students 

 in attendance frequently exceeded one hundred.' 



' De Morgan's exposition combined excellences of the 

 most varied kinds. It was clear, vivid, and succinct rich 

 too with abundance of illustration always at the command 

 of enormously wide reading and an astonishingly retentive 

 memory. A voice of sonorous sweetness, a grand forehead, 

 and a profile of classic beauty, intensified the impression 

 of commanding power which an almost equally complete 

 mastery over Mathematical truth, and over the forms of 

 language in which he so attractively arrayed it, could not 

 fail to make upon his auditors. Greater, however, than 

 even these eminent qualities were the love of scientific 

 truth for its own sake, and the utter contempt for all 



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