His Method of Working. 129 



away all the leaves which did not relate to his work. 

 When books were rilled with notes he frequently 

 added an index at the end with the number of the 

 pages marked, and thus had a list of the subjects in 

 which he was interested, so at short notice he could 

 command all the material bearing on a certain point 

 in his possession. Fortunately Darwin had ample 

 means, which enabled him to devote his entire time 

 to scientific work without the distraction which 

 would naturally have come from an attempt to 

 make his labour pay a yearly dividend or income. 

 His habits were simple and methodical, and within 

 a short distance of the hum and bustle of the great 

 city of London he carried on his experiments for 

 forty years, happy in the companionship of such 

 men as Huxley, Hooker, Owen, Lubbock, and 

 others, producing results that will place him among 

 the leaders of science as long as time endures. 



One of Darwin's experiments will illustrate his 

 method of work, and the consideration and labour 

 which he gave to it. While on a visit to his uncle 

 the latter suggested that the supposed sinking of 

 stones on the surface was really due to the castings 

 of earth-worms. The idea made so strong an impres- 

 sion upon the mind of the naturalist, that he read the 

 paper previously referred to on the subject before 

 the Geological Society. When the farm at Down 

 was secured, in 1842, he set apart some of the ground 

 for his experiment, which was to cover a part of the 

 field with broken chalk, and note, among other things, 

 the disappearance of the layer through the agency of 

 the worm castings. The plat was covered in De- 

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