Sentence:  ... he was propounding an improvement of Professor Armstrong's Heuristic method, whereby at the cost of three or four hundred pounds' worth of apparatus, a total neglect of all other studies and the undivided attention of a teacher of exceptional gifts, an average child might with a peculiar sort of <WSD>thumby</WSD> thoroughness learn in the course of ten or twelve years almost as much chemistry as one could get in one of those objectionable shilling text-books that were then so common…. 
Meaning of the word marked with <WSD> tags:  Clumsy, awkward, maladroit, not dextrous, all thumbs