facts and sequences of nature. This knowledge is especially connected with industries, arts and crafts where observation of materials and processes is required for successful action, and where action is so continuous and regular that spasmodic magic will not suffice. Extravagantly fantastic notions are eliminated because they are brought into juxtaposition with what actually happens. The sailor is more likely to be given to what we now term superstitions than say the weaver, because his activity is more at the mercy of sudden change and unforeseen occurrence. But even the sailor while he may regard the wind as the uncontrollable expression of the caprice of a great spirit, will still have to become acquainted with some purely mechanical principles of adjustment of boat, sails and oar to the wind. Fire may be conceived as a supernatural dragon because some time or other a swift, bright and devouring flame called before the mind's eye the quick-moving and dangerous serpent. But the housewife who tends the fire and the pots wherein food cooks will still be compelled to observe certain mechanical facts of draft and replenishment, and passage from wood to ash. Still more will the worker in metals accumulate verifiable details about the conditions and consequences of the operation of heat. He may retain for special and ceremonial occasions traditional beliefs, but everyday familiar use will expel these conceptions for the greater part of the time, when fire will be to him of uniform and prosaic behavior, controllable by practical relations of cause and effect. As the arts and crafts develop and become more elaborate, the body of positive and tested knowledge enlarges, and the sequences observed become more complex and of greater scope. Technologies of this kind give that common-sense knowledge of nature out of which science takes its origin. They provide not merely a collection of positive facts, but they give expertness in dealing with materials and tools, and promote the development of the experimental habit of mind, as soon as an art can be taken away from the rule of sheer custom.