Before setting out upon any research, the careful man of science sets himself to study "the literature of the subject" as he calls it. He delves into all sorts of out-of-the-way periodicals to ascertain what such a man has written upon such a point. All this he does in order that he may avoid doing a piece of work over again unnecessarily: _unnecessarily_, for it maybe actually necessary to repeat it, if it is of very great importance and if it has not been repeated and verified by other observers. Further, he delves into this literature because it is thus that he hopes to avoid the many blind alleys which branch off from every path of research, delude their explorer with vain hopes and finally bring him face to face with a blank wall. In a word the inquirer consults his authorities and when he finds them worthy of reliance, he limits his freedom by paying attention to them. He does not say: "How am I held in bondage by this assertion that the earth goes round the sun," but accepting that fact, he rejects such of his conclusions as are obviously irreconcilable with it. Surely this is plain common sense and the man who acted otherwise would be setting himself a quite impossible task. It is the weakness of the "heuristic method" that it sets its pupils to find out things which many abler men have spent years in investigating. The man who sets out to make a research, without first ascertaining what others have done in that direction, proposes to accumulate in himself the abilities and the life-work of all previous generations of labourers in that corner of the scientific vineyard. There is a somewhat amusing and certainly interesting instance of this which will bear quotation. The late Mr. Grant Allen, who knew something of quite a number of subjects though perhaps not very much about any of them, devoted most of his time and energies (outside his stories, some of which are quite entertaining) to not always very accurate essays in natural history. One day, however, his evil genius prompted him to write and, worse still, to publish a book entitled _Force and Energy: A Theory of Dynamics_, in which he purported to deal with a matter of which he knew far less even than he did about animated nature. Mark the inevitable result! A copy of the book was forwarded to the journal _Nature_, and sent by its editor to be dealt with by the competent hands of Sir Oliver (then Professor) Lodge.[27]