And if Darwin was insistent upon accuracy in records, he was also extraordinarily thorough and exact in mathematical matters and measurement. He speaks of abstract mathematics as having been one of the neglected elements of his education,[30] but he shunned no amount of pains and toil in calculating, wherever he felt it necessary to work out his results. In his books which record the investigation of detail there is an almost incredible amount of slow and careful research involving exact counting and weighing and measuring. ‘I was compelled to count under the microscope above 20,000 seeds of _Lythrum salicaria_,’ he says casually in one instance,[31] and there are innumerable others of the same kind. In all these calculations the possibility of error haunts him and he does his best to eliminate it, yet still the possibility is there: ‘Although I always am endeavoring to be cautious and to mistrust myself, yet I know well how apt I am to make blunders.’[32] If he blundered, what shall be said of some of us? Most interesting and characteristic is the trait, pointed out by his son, that he assumed with singular naïveté the absolute accuracy of the instruments that came to him: ‘He had great faith in instruments, and I do not think it naturally occurred to him to doubt the accuracy of a scale or measuring glass.’[33] Yet further, ‘it was characteristic of him that he took scrupulous pains in making measurements with his somewhat rough scales.’[34] As he was exact and particular in calculation and measurement, so he shrank from no amount of detail, did not hesitate to carry his investigations to the last point of minuteness, whenever the full and solid breadth of result demanded it. Apparently nothing escaped him. It was not only what he was looking for, but he noted and seized oddities and exceptions for their larger bearing and for future profit. As his son says, ‘A point apparently slight and unconnected with his present work is passed over by many a man almost unconsciously with some half-considered explanation, which is in fact no explanation. It was just these things that he seized on to make a start from.’[35] Thus, on any subject that came up, his memory or his notes could almost always be appealed to. As Sir Thomas Farrer puts it, ‘What interested me was to see that on this as on almost any other point of detailed observation, Mr. Darwin could always say, “Yes, but at one time I made some observations myself on this particular point; and I think you will find, etc., etc.”’[36]