394 TEE SCIENTIFIC MONTHLY
large to preclude a not infrequent inadvertent assemblage of favorable conditions^ was nevertheless sufficiently large to render their control at will a scientific problem which, to man at this stage of his develop- ment and facilities^ must have been one of very formidable dimensions. We only know that it was surmounted, perhaps not once but many times. The laborious individual steps and the flashes of intellectual insight which led up to the conquest are necessarily lost to us forever.
If any of my readers is inclined to think that I place too high a valuation upon the intellectual exertions of primitive man, let him but try, as the author has done, with the powerful assistance of a modern jack-knife and all the inspiration afforded by familiar models, to make a practicable fire-stick or a bow and arrow which shall be something more than a toy. At the end of a few hours or days of endeavor he will have acquired a very enhanced respect for his ancestors.
The development of agricxdture in its earliest stages called for foresight and prudence, but not, perhaps, for such extreme exertions of investigative ability as the inventions upon which I have hitherto been dwelling. Directly it passed the first stage of collecting edible plants in a convenient neighborhood, however, the development of agriculture demanded its share of observation, comparison, deduction and trial. The relationship of moisture to the growth of plants would be observed by a comparison of relative growth in different localities or patches of the same locality. In the neighborhood of rivers this would lead to irrigation and that in turn to the acquirement of some of the fundamental notions of hydromechanics. It would be observed, for example, that water would not flow up-hill except under pressure, that a '^head^' of water was capable of exerting pressure, that the water in two connected vessels tends to reach the same level in each, etc. The transition from a recognition of these principles to the formulation of the erroneous but exceedingly useful doctrine of the incompressibility of fluids required only the incorporation of mathe- matical conceptions which were destined to be the bye-product of the apparently unrelated enterprises of astronomy and architecture.
The development of architecture is generally traced from the tent of skins and the cabin of logs. Directly more ambitious edifices came to be attempted, however, a knowledge of the strength of materials and the relationship of stress and strain to structure became an im- perative prerequisite of success, and by the now familiar process it was acquired. As the constructional details of a large edifice were too numerous to be simultaneously borne in mind, design became a neces- sary part of architecture, and geometry sprang from design.
The stars must necessarily have riveted the restless curiosity of man from a very early period in his development. Their utility as landmarks and as guides must speedily have impressed themselves upon
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