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Page 40 - I have long held an opinion, almost amounting to conviction, in common I believe with many other lovers of natural knowledge, that the various forms under which the forces of matter are made manifest have one common origin; or, in other words, are so directly related and mutually dependent, that they are convertible, as it were, one into another, and possess equivalents of power in their action.
Page 41 - I cannot,' he says, at the end of his first paper on magne-crystallic action, ' conclude this series of researches without remarking how rapidly the knowledge of molecular forces grows upon us, and how strikingly every investigation tends to develop more and more their importance, and their extreme attraction as an object of study. A few years ago magnetism was to...
Page 179 - A bar magnet is held vertically and two equal straight bits of soft iron wire hang downwards from its lower end. The lower end of each of these wires can by itself hold up a small scrap of iron ; but if the lower ends of both wires touch the same scrap of iron at the same time, they do not hold it up. What is the reason of this ? (2, 1881.) 10.
Page 179 - A pewter pot is insulated and electrified ; if you touch it at different parts with a penny stuck to the end of a rod of sealing-wax, what part of the pot will give the greatest quantity, and what part the least quantity of electricity to the penny ? 8.
Page 171 - An apple held in the hand and struck with a fox's brush shows no signs of electrical action ; suspended by a string of silk and struck with the brush it becomes electrified, attracting light bodies and causing the leaves of the electroscope to diverge. Explain these results.
Page 171 - A sheet of hot paper is placed on a hot board, and indiarubber is passed briskly over it. Two strips are cut from the paper and held up close and parallel to each other. How will they act upon each other? A glass rod, rubbed with silk, repels both the strips ; what is the inference ? 7.
Page 176 - Why is less force required to pull a small iron rod away from the poles of a powerful horse-shoe magnet than would be required to pull a thick bar of iron away from the poles of the same magnet ? 4.
Page 176 - A current passing though a long wire is so weak that, when the wire is stretched over, and parallel to, a suspended magnetic needle, the needle is not perceptibly deflected. Describe and explain an arrangement which would enable you to obtain a movement of the needle by the action of the current.
Page 179 - If you were required to make a model to illustrate the magnetic properties of the earth by putting a bar magnet inside a ball of clay, show by a sketch how you would place the magnet, and explain how the magnetic properties of the model would answer to those of the earth.
Page 171 - I whisk a bit ot vulcanized india-rubber with a fox's brush. Holding the sealing-wax as a handle, I lay the penny, or half-crown, flat on the indiarubber. What is the condition of the coin ? I touch the coin, what occurs ? I lift it by the handle, what is its condition?