So the wealth of the world, as measured by its productive labour and its power of supporting human life, increased vastly; and its population increased vastly therewith. At the same time it is very much to be doubted whether the happiness of the people generally increased. But gradually, by coming together into the combinations of which I have spoken, and so being able to say to the employer, "You will not get any of us to work for you unless you give us so much money for so many hours of work"--gradually, by this argument, and sometimes by carrying it into actual effect by "striking," and ceasing to work altogether, they have won better and better terms for themselves. Employers now recognise that the workman should receive such a wage as the profits of the industry in which he is engaged suffice to pay him. Perhaps some of our more recent labour trouble is due to the worker's claim to be paid a larger wage than the industry can afford, if it is to turn out its products at a cost at which any one will buy them. And if it cannot turn them out at such cost, it must, and it will, stop producing them altogether; so that thus the workman is unemployed. Further remarkable discoveries followed. Coal gas was used for lighting, and was later superseded by electricity. Electricity was used to give motion to machinery in place of steam. The telegraph was invented and the telephone. Engines were constructed to work by means of petrol firing within themselves--by internal combustion, as it is called--whence came motor-cars and flying machines. Wireless telegraphy made its marvellous appearance. {193} Radio-activity with its terrifying possibilities has been discovered. But no one, not even all of these together, made a new start, with a new chapter in the story, at all in the same sense as did the application of the power of steam. All these others were rather in the nature of a development from that starting-point. They were further successful efforts on the part of man to "harness," as has been said--which means, to control for his own purposes--the forces of Nature. [Sidenote: Evolution] There was, however, one scientific discovery of about the middle of the nineteenth century, which is of very remarkable interest in man's history, because it gave quite a new direction to his thoughts about his own origin. It is that discovery which is summed up in the word "Evolution," and which is associated especially with the name of Darwin.