But neither curiosity nor even the ardor of research will go very far, unless backed up by a habit of enormous and persistent industry. It is not the showy spurts that count, the bursts of application for a few weeks or months. It is the long, assiduous unbroken labor, such as thousands of scientists are giving in hundreds of laboratories, without prospect of distinction, without hope of immediate reward, simply from pure love of the work itself. And this toil is expended not only on the practical inventions, which are expected to produce comparatively quick and often astonishing commercial results, but on pure science, abstract investigation of speculative problems, which even if solved, will not change the practical conditions of life in the slightest degree. Although Darwin sometimes questioned the wisdom of spending so many years on his petty barnacles, he knew that the work was immensely valuable to him in the pure discipline of labor. At any rate it taught him a profound and sincere respect for those who were doing such work steadily, cheerfully, unendingly, without looking to anything else whatever: ‘He would never allow a depreciatory remark to pass unchallenged on the poorest class of scientific workers, provided that their work was honest, and good of its kind.’[129] There are times when labor is attractive, when you feel like it and like nothing else, and are ready to plunge into it with a furious zeal. There are other times when you are dispirited and discouraged, when the labor seems worthless and the effort impossible, or when you have a sheer desire to drop it altogether and go play. Sir Walter Scott, one of the great workers of the world, tells us that if any one set him a task to do, even agreeable in itself, the result immediately was an unbounded desire to do something else. The real spirit of industry shows in sticking through these periods of discouragement and distraction, and the worker who accomplishes is he who does not heed them. It is one of the striking things about Darwin that he kept up work all his life in this spirit, in spite of all limitations and obstacles, and as a pure amateur in the best sense of the word. It is true that he himself points out what a benefit it was to him not to be professionally tied to any duties: ‘If I had any regular duties, like you and Hooker, I should do nothing in science.’[130] But it is also true that few men with plenty of money, with plenty of temptation to amusement of every sort, would have stuck to their chosen work with the ardor and also the long, persistent system, which Darwin kept up to the end.