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time his much loved son-in-law, became his assistant in the Labora- 

 tory, and finally, his eminent successor. Bonders continued in these 

 new circumstances to display the same marvellous productiveness as 

 heretofore, and to animate, by his influence and example, the younger 

 men attracted to him, often from distant countries. He delighted, as 

 he had ever done, to make them taste the joy of becoming themselves 

 the authors of some original work of value, and to engage their 

 interest and help in his own laborious and systematic inquiries into 

 whatever promised to benefit mankind in t.he sphere of the sciences 

 he was cultivating. 



No better example of this generous ardour of pursuit could be 

 adduced than his method of dealing with the subjects of the Colour 

 Sense and of Colour Blindness, then more and more attracting atten- 

 tion in relation to the public safety. It exhibits very aptly his many- 

 sided excellence. While acquainting himself with the ideas of his 

 predecessors, he first statistically ascertained, with accuracy for him- 

 self, the broader facts, engaging for this the aid of his younger 

 colleagues and pupils. The delicate instruments which he was from 

 time to time contriving in the course of his researches bearing on the 

 theory of the Colour Sense and its defects, as on other subjects,* 

 were constructed in a special department of his laboratory by the 

 mechanician Kagenaar, whom he had reared from a youth and made 

 his friend. His theoretical conclusions, as they were reached, were 

 published in papers of permanent value.f Meanwhile he was also 

 calling the attention of the higher officials of the railway and sea 

 services, of his own and other countries, by all the means within his 

 power, to the responsibilities they lay under for the lives of the com- 

 munity, in the matter of Colour Blindness ; was framing rules for 

 their acceptance, which they might suitably enforce ; and pressing his 

 conclusions to their final consequences in practical life, with such 

 directness, moderation, and good sense, as compelled the attention 

 and assent of administrators and statesmen. And that he might not 

 fail in his immediate object of effecting a present benefit, he further, 

 for many years personally undertook, without remuneration, the very 

 considerable labour of superintending the carrying out of this matter 

 on the railways of Holland, examining scrupulously into the more 

 doubtful instances of supposed defect, so as to prevent injustice to 

 individuals, and in every way facilitating the adoption of the new 

 rules which he had suggested. No wonder that his countrymen, 



* Many of these instruments were exhibited at South Kensington in the Loan 

 Collection of Scientific Apparatus, 1876. 



t His views of that day " On Colours and Colour Blindness " were well summarised 

 by himself in the theatre of the Lucasian Professor at Cambridge, August, 1880, 

 Sir George Or. Stokes being present. See ' Brit. Med. Journ.,' 13th November, 

 1880. 



