We can go on endlessly with our speculations on the evolution of tools and machinery up to the time when historians began to record the mechanical achievements of man. Unfortunately even after historians began to write they were so filled with admiration for the destructive work of man that they had no time to record his constructive work. The warrior who spread havoc and terror received all the glory, and his deeds were written on parchment, inscribed in clay and carved in stone; but the humble artisan was not worthy of mention. Even when the science of mechanics came to be studied, it was shrouded in a veil of mystery, and it was beneath the dignity of the man of science to impart his knowledge to the artisan. There was a lack of cooperation between science and industry that has persisted to a certain extent even up to the present time. Some of the most ingenious inventions of the ancients were employed by a corrupt and crafty priesthood to produce apparently miraculous effects and hoodwink the general public; and so, in looking back to the early days of mechanics, we are obliged to draw upon our imagination to trace its evolution, supplementing this by a study of the tools of primitive people of more recent time. Practically every form of hand tool we now use must have been known to the ancient artisan. INVENTION OF THE WHEEL We are not going to attempt to write a history of the evolution of machinery, but there is one invention whose origin is lost in the remote prehistoric ages which deserves more than passing attention. It is a pity that we have no clue as to who invented the wheel or how this most important element that enters into the construction of nearly all machinery was evolved. The invention called for a remarkable degree of originality. There is nothing like a wheel in nature. Levers we have in our own physical frame. But a wheel is something that is distinctly a human creation. Whoever invented it must have been a real genius, a James Watt or a Thomas Edison of his day. Certainly we owe more to the invention of the wheel than we do even to so revolutionary a machine as the steam engine, or the flying machine. How it was ever first conceived is a mystery. Maybe this primeval genius got his idea from seeing a stone rolling downhill, or he may have seen a tumbling weed rolling along the ground before the wind. It may be that the forerunner of the wheel was a roller shaped out of a log, for certainly primitive civilization must have advanced enough to have known how to hew timber before it would have been capable of fashioning a wheel. Some observant man might have noticed that he could drag a heavy timber over a rolling log much more easily than he could along the bare ground, and gradually the roller evolved into a wheel.