The operation of the motor is so simple that it requires very little human labour. When power is desired, the reflector must be swung into focus--that is, pointed exactly toward the sun--which is done by turning a crank. This is not beyond the power of a good-sized boy. There is an indicator which readily shows when a true focus is obtained. This done, the reflector follows the sun closely all day. In about an hour the engine can be started by a turn of the throttle-valve. As the engine is automatic and self-oiling, it runs without further attention. The supply of water to the boiler is also automatic, and is maintained at a constant height without any danger of either too much or too little water. Steam-pressure is controlled by means of a safety-valve, so that it may never reach a dangerous point. The steam passes from the engine to the condenser and thence to the boiler, and the process is repeated indefinitely. Having now the solar motor, let us see what it is good for, what is expected of it. Of course when the sun does not shine the motor does not work, so that its usefulness would be much curtailed in a very cloudy country like England, for instance; but here in Southern California and in all the desert region of the United States and Mexico, to say nothing of the Sahara in Africa, where the sun shines almost continuously, the solar motor has its greatest sphere of usefulness, and, indeed, its greatest need; for these lands of long sunshine, the deserts, are also the lands of parched fruitlessness, of little water, so that the invention of a motor which will utilise the abundant sunshine for pumping the much-needed water has a peculiar value here. [Illustration: The Brilliant Steam Boiler Glistens in the Centre.] The solar motor is expected to operate at all seasons of the year, regardless of all climatic conditions, with the single exception of cloudy skies. Cold makes no difference whatever. The best results from the first model used in experimental work at Denver were obtained at a time when the pond from which the water was pumped was covered with a thick coating of ice. But, of course, the length of the solar day is longer in the summer, giving more heat and more power. The motor may be depended upon for work from about one hour and a half after sunrise to within half an hour of sunset. In the summer time this would mean about twelve hours' constant pumping.