Elementary Physics: An Introduction to the Study of Natural Philosophy

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Reeve and Benham, 1851 - Physics - 486 pages
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Page 371 - I had often, in the pride of half knowledge, smiled at the means frequently employed by gardeners, to protect tender plants from cold, as it appeared to me impossible, that a thin mat, or any such flimsy substance, could prevent them from attaining the temperature of the atmosphere, by which alone I thought them liable to be injured. But, when I had learned, that bodies on the surface of the earth become, during a still and serene night, colder than the atmosphere, by radiating their heat to the...
Page 409 - To the same degree of Refrangibility ever belongs the same colour, and to the same colour ever belongs the same degree of Refrangibility.
Page 409 - ... follows, that the orange and green rays of the spectrum, though they cannot be decomposed by prismatic refraction, can be decomposed by absorption, and actually consist of two different colours possessing the same degree of refrangibility.
Page 257 - ... the quantity of electrolyte decomposed, must be the equivalents of each other. The action in each cell, therefore, is not to increase the quantity set in motion in any one cell, but to aid in urging forward that quantity, the passing of which is consistent with the oxidation of its own zinc ; and in this way it exalts that peculiar property of the current which we endeavour to express by the term intensity, without increasing the quantity beyond that which is proportionate to the quantity of...
Page 410 - By absorbing the excess of any color at any point of the spectrum above what is necessary to form white light, we may actually cause white light to appear at that point, and this white light will possess the remarkable property of remaining white after any number of refractions, and of being decomposable only by absorption.
Page 324 - ... all those planets whose internal structure admits of such a difference. Yet, allowing all this, the main difficulty seems not to be overcome, but merely removed from the eyes to a greater distance ; for the question may still be asked, with equal justice, whence did the sun acquire its magnetic force ? And if from the sun we have recourse to a central sun, and from that again to a general magnetic direction throughout the universe, having the Milky Way for its equator, we but lengthen an unrestricted...
Page 205 - Now it is wonderful to observe how small a quantity of a compound body is decomposed by a certain portion of electricity. Let us, for instance, consider this and a few other points in relation to water. One grain of water, acidulated to facilitate conduction, will require an electric current to be continued for three minutes and three quarters of time to effect its decomposition, which current must be powerful enough to retain a platina wire TúT of an inch in thickness*, red hot, in the air during...
Page 410 - ... out of place here to detail, I conclude that the solar spectrum consists of three spectra of equal lengths, viz. a red spectrum, a yellow spectrum, and a blue spectrum. The primary red spectrum has its maximum of intensity about the middle of the red space in the solar spectrum, the primary yellow spectrum has its maximum in the middle of the yellow space, and the primary blue spectrum has its maximum between the blue and the indigo space. The two minima of each of the three primary spectra coincide...
Page 451 - These discoveries bear most strikingly upon all my experiments ; and, at the same time as they appear to confirm in a most satisfactory manner the conclusions to which my results have led me, they point to an order in the natural arrangement which is singularly interesting. In the spring, when seeds germinate and young vegetation awakes from the repose of winter, we find an excess of that principle which imparts the required stimulus ; in the summer, this exciting agent is counterbalanced by another...
Page 441 - Upon all those bodies on which liyht exerts a direct and determinate influence, aa upon the organized compounds, we find that the changes due to actinic power are but slightly interfered with, whereas upon all those inorganic bodies which undergo a change when exposed to the solar chemical radiations, that change being entirely due to actinism, light acts as a powerfully interfering agent. The conditions under which these antagonistic forces — light and actinism — operate upon each other are...

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