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NATURE 



[Oct. 24, 1889 



agreement or disagreement, of most cordial interest in 

 each other, and yet we did not know each other's faces. 

 I met him about 1830 at Babbage's breakfast-table, and 

 there for the only time in our lives we conversed. I saw 

 him a long way off at the dinner given to Herschel about 

 1838, on his return from the Cape, and there we were not 

 near enough, nor on that crowded day could we get near 

 enough to exchange a word ; and this is all I ever saw, 

 and, so it has pleased God, all I shall see in this world, 

 of a man whose friendly communications were among 

 my greatest social enjoyments and greatest intellectual 

 treats." 



Hamilton was scrupulously sensitive about the feelings 

 of others, and in his scientific work he took the most 

 elaborate precautions that every particle of credit should 

 be duly assigned to every mathematician whose labours 

 had in the minutest extent anticipated his own. He had 

 high personal courage and a keen sense of honour. It 

 is recorded that he sent a hostile message to one who 

 had challenged his veracity, and a due apology was 

 exacted. The only approach that Hamilton ever had to 

 a controversy about priority arose in the case of the dis- 

 covery of conical refraction. MacCullagh put forward a 

 claim to have virtually anticipated Hamilton. The sound 

 judgment and lofty sense of right which were so charac- 

 teristic of Humphrey Lloyd here averted what would have 

 been an unpleasant dispute, and MacCullagh withdrew his 

 pretension. 



De Morgan says that in Hamilton's youth he used to 

 be styled among his playmates the "defender of the 

 absent," and from the same source we learn : — 



"He relished the extremes both of simplicity and 

 splendour ; though in his own habits and manners as plain 

 as possible, he thought much of the comforts of others 

 and lightly of his own. When some housebreakers were 

 caught on the premises and detained until they could be 

 carried before a magistrate, he amused his family by 

 directing that the fellows should be asked whether they 

 preferred tea or milk for breakfast. A full memoir of his 

 private and public life would present a genial combination 

 of intellectual greatness, moral goodness, and piquant 

 peculiarity of thought and manner, all brightened by 

 never-ceasing benevolence of feeling, and toned by rare 

 gentleness of manner." 



Hamilton has left behind him an enormous bulk of 

 manuscripts, of which not less than sixty great volumes 

 have been deposited in the College Library. There are 

 also many other papers unpublished, as, for instance, a 

 stupendous letter to Dr. Hart, which contained about 240 

 large folio pages and a postscript of 60 additional. 



The distinctive feature of this third volume of his life is 

 the De Morgan correspondence, which, like the corre- 

 spondence between Bessel and Olbers, will retain a per- 

 manent value. The opening letter of the series is from De 

 Morgan, on May 8, 1841 , in which he says : " I hardly know 

 whether you remember that we made a little personal 

 acquaintance some twelve years ago, when you were in 

 London." The last is also from De Morgan, and the date 

 February 3, 1865, relative to an application for a pension 

 for the widow of the late Prof. Boole. 



The correspondence, though largely on matters mathe- 

 matical, ranges over a multitude of topics, classical and 

 literary, logical and metaphysical, humorous and do- 

 mestic. It sometimes glances at theology, occasionally 

 condescends to refer to a practical question like the 



decimal system, but is almost wholly free from any refer- 

 ence to what are now generally known as the experi- 

 mental or natural sciences, though we do indeed read of 

 an electro-magnetic quaternion. From such an astound- 

 ing mass of 400 pages it is difficult to cull passages which 

 shall be regarded as samples. The collection is too 

 heterogeneous to admit of such a process. It is, however, 

 impossible not to feel how admirably the biographer has 

 accomplished this part of his task. He has extracted 

 from a mighty bulk of correspondence a collection so 

 interesting that, after reading them through, we do not see 

 any which we could wish to have been omitted. 



It was three years after the interchange of letters had 

 begun, and when Hamilton was thirty-nine years old, 

 that De Morgan writes (p. 258) :— 



" I hope you are well, and taking care of yourself. 

 Nobody gives you a good character in the second 

 particular. 



"The Astronomer-Royal in this country always lays 

 down his work the moment he feels wrong, and plays 

 till he feels right again. You have too much of our stock 

 of science invested in your head to be allowed to commit 

 waste. You are only tenant for life, and posterity has 

 the reversion ; and I don't see why you should not be 

 compelled to keep yourself in repair." 



Traditions of the state of Hamilton's study are still 

 current. The awful masses of books and papers accu- 

 mulated on the floor to such an extent that a lane had to 

 be preserved for the perambulations of the Professor, who 

 did much of his work standing at a blackboard, or walk- 

 ing up and down. Thus we can understand him writing 

 to De Morgan on October 3, 1849 (p. 279) :— 



" If I lay a letter out of my hands for a few hours, 

 without answering it, I am sure to find that it has been 

 swept away and covered up, for the time, by the Charyb- 

 dis of my other papers. No doubt, every such missing 

 treasure may be expected, at some future time, to emerge 

 to view, and may then be suddenly seized, by a bold and 

 ready hand. Thus, from month to month, or at least 

 from year to year, I find a note or two of yours eddying 

 upward to the light ; but, for the instant, your last long 

 (and welcome) letter is invisible. However, I remember 

 much of its contents, and shall send something now in 

 answer to one, at least, of its ' loose thoughts.' '"' 



As already mentioned, De Morgan could never be in- 

 duced to devote himself sufficiently to quaternions to 

 understand them. He often alludes to this, thus writing 

 on October 1 1, 1849 (p. 283) :— 



" Nothing about quaternions will bore me, if I can 

 only make it bore through me. Ink must be cheap in 

 Ireland if you can afford to waste it on such a supposition 

 as that." ' 



Many amusing references are made by De Morgan to 

 the contrast between his friendship to the Sir William 

 Hamilton of Dublin, and his notorious controversies 

 with the Sir William Hamilton of Edinburgh. Thus, 

 on April 14, 1850 (p. 286) :— 



" Be it known unto you that I have discovered that 

 you and the other Sir William Hamilton are reciprocal 

 polars with respect to me (intellectually and morally, for 

 the Scotch baronet is a Polar bear, and you, I was gomg 

 to say, are a Polar gentleman, only I thought perhaps 

 you might go and say I called you an Esquimaux). The 

 intellectual polarity is of the kind, (l>^{.x) = - x. When 

 I send a bit of investigation to Edinburgh, the William . 



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