Popular lectures on scientific subjects, tr. by E. Atkinson. [1st], Volume 1 |
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Popular Lectures on Scientific Subjects, Tr. by E. Atkinson. [1st] Hermann Ludwig F. von Helmholtz No preview available - 2018 |
Popular Lectures on Scientific Subjects, Tr. by E. Atkinson. [1st] Hermann Ludwig F. Von Helmholtz No preview available - 2015 |
Common terms and phrases
action animals appear become blue bodies bright carbon carbonic acid changes chemical affinity chemical forces Col du Géant colour combination combustion compressed conception corresponding crystalline lens depends direction disc earth effect electrical electrical currents excited experiments external objects fact fall fibres field of vision friction fundamental tone glacier Goethe hammer Hence human illumination impression instrument investigation kind labour light look machine mass means mechanical force melt Mer de Glace motion moving musical natural forces natural philosopher observation optic nerve organs oxygen peculiar perception phenomena physical sciences physiology pieces of ice pitch possible present pressure processes produced quantity of heat rays recognise result retina scientific seen sensations sensations of sight senses separate sight snow space stereoscopic string surface temperature theory theory of colour tion upper partial tones velocity vibrations violet vis viva weight
Popular passages
Page 180 - And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness. And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
Page 156 - The nature of the problem was quite calculated to entice poring brains, to lead them round a circle for years, deceiving ever with new expectations, which vanished upon nearer approach, and finally reducing these dupes of hope to open insanity. The phantom could not be grasped. It would be impossible to give a history of these efforts, as the clearer heads, among whom the elder Droz must be ranked, convinced themselves of the futility of their experiments, and were naturally not inclined to speak...
Page 180 - Neither is the Mosaic tradition very divergent, particularly when we remember that that which Moses names heaven, is different from the blue dome above us, and is synonymous with space, and that the unformed earth and the waters of the great deep, which were afterwards divided into waters above the firmament and waters below the firmament, resembled the chaotic components of the world : — ' In the beginning God created the heaven and the earth.
Page 154 - Its wheel-work is so complicated, that no ordinary head would be sufficient to decipher its manner of action. When, however, we are informed that this boy and its constructor, being suspected of the black art, lay for a time in the Spanish Inquisition, and with difficulty obtained their freedom, we may infer that in those days even such a toy appeared great enough to excite doubts as to its natural origin. And though these artists may not have hoped to breathe into the creature of their ingenuity...
Page 188 - ... come when the comet will strike the sun ; and a similar end threatens all the planets, although after a time, the length of which baffles our imagination to conceive of it. But even should the existence of a resisting medium appear doubtful to us, there is no doubt that the planets are not wholly composed of solid materials which are inseparably bound together. Signs of the existence of an atmosphere are observed on the Sun, on Venus, Mars, Jupiter, and Saturn. Signs of water and ice upon Mars...
Page 191 - What the museums of Europe show us of the remains of Egypt and Assyria we gaze upon with silent astonishment, and despair of being able to carry our thoughts back to a period so remote.
Page 162 - ... apparatus generate no force, but simply yield up the power communicated to them by natural forces,— falling water, moving wind, or by the muscles of men and animals. After this law had been established by the great mathematicians of the last century, a perpetual motion, which should make use solely of pure mechanical forces, such as gravity, elasticity, pressure of liquids and gases, could only be sought after by bewildered and ill-instructed people.
Page 171 - Further, from the fact that no portion of force can be absolutely lost, it does not follow that a portion may not be inapplicable to human purposes. In this respect the inferences drawn by William Thomson from the law of Carnot are of importance. This law, which was discovered by Carnot during his endeavours to ascertain the relations between heat and mechanical force, which, however, by no means belongs to the necessary consequences of the conservation of force, and which Clausius was the first...
Page 182 - ... gnawed the rocks, carried away the light earth, and thus performed its part in the geologic changes of the earth; perhaps, besides all this it has driven our watermill upon its way. If the heat of the sun were withdrawn, there would remain only a single motion of water, namely, the tides, which are produced by the attraction of the sun and moon. How is it, now, with the motions and the work of organic beings. To the builders of the automata of the last century, men and animals appeared as clockwork...
Page 157 - The value of manual labor is determined partly by the force which is expended in it (a strong laborer is valued more highly than a weak one), partly however, by the skill which is brought into action. A machine, on the contrary, which executes work skilfully, can always be multiplied to any extent; hence its skill has not the high value of human skill in domains where the latter cannot be supplied...