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In the same manner, an inventor makes a model before he constructs the full-sized machine; the chemist wastes some chemicals—the farmer wastes some seeds and land—to try out an idea.
同样地,发明家制造完整的机器之前总要先造个模型,化学家尝试新的想法总要浪费一些化学制品,农民尝试新了想法总要浪费一些种子和土地一样。