Popular Lectures on Science and Art: Delivered in the Principal Cities and Towns of the United States, Τόμος 2Greeley & McElrath, 1846 |
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air-pump angle apparent magnitude appear applied atmospheric pressure attached axis axle beam body boiler boiling boiling point bottom bulb called cause centre of gravity cock combustion communication condenser conductor constellation constructed continued crank cylinder degree descend diameter diminished direction distance double star downward effect elastic electricity engine equal experiments feet fluid force fulgurites greater heat inclined plane increased instrument latent heat length lever light liquid machine magnet magnitude manner mass mechanical mercury meridian metal motion moving power necessary object observed particles pass phenomena pinion pipe piston piston-rod placed plane position principle produced proportion pulley quantity raised receiver rendered represented in fig resistance revolution revolve rope screw sensible heat Sir William Herschel slide space stars steam steam-engine stroke sufficient suppose surface telescope temperature thermometer tion tube upward vacuum valve vapor velocity vertical vessel weight wheel wire
Δημοφιλή αποσπάσματα
Σελίδα 75 - In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.
Σελίδα 75 - And God remembered Noah, and every living thing, and all the cattle that was with him in the ark: and God made a wind to pass over the earth, and the waters assuaged...
Σελίδα 366 - Allotted there; and other suns perhaps, With their attendant moons, thou wilt descry, Communicating male and female light, Which two great sexes animate the world, Stored in each orb perhaps with some that live.
Σελίδα 375 - Herschel, whose powerful telescopes have effected a complete analysis of this wonderful zone, and demonstrated the fact of its entirely consisting of stars. So crowded are they in some parts of it, that by counting the stars in a single field of his telescope, he was led to conclude that 50000 had passed under his review in a zone two degrees in breadth, during a single hour's observation.
Σελίδα 388 - I have seen double and treble nebulae variously arranged; large ones with small, seeming attendants ; narrow, but much extended lucid nebulae or bright dashes; some of the shape of a fan, resembling an electric brush issuing from a lucid point; others of the cometic shape, with a seeming nucleus in the centre, or like cloudy stars surrounded with a nebulous atmosphere. A different sort, again...
Σελίδα 284 - This is the case when pins, bolts or nails are used for binding the parts of structures together ; in which case, were it not for the friction, they would recoil from their places, and fail to produce the desired effect. Even when the wedge is used as a mechanical engine, the presence of friction is absolutely indispensable to its practical utility. The power, as has already been stated, generally acts by successive blows, and is therefore subject to constant intermission, and, but for the friction,...
Σελίδα 386 - ... which may be, and probably is, stardust, but which the powers of the twenty-feet telescope show only as a general illumination of the field of view, forming a bright ground on which the other objects are scattered. Some of the objects in it are of very singular and incomprehensible forms; the chief one especially...
Σελίδα 432 - I mentioned to you a method of still doubling the effect of the steam, and that tolerably easy, by using the power of steam rushing into a vacuum, at present lost.
Σελίδα 242 - ... truth is made. For, in investigating the laws which regulate the several effects just mentioned, we are compelled to proceed upon a new group of false suppositions. To determine the laws which regulate the friction of surfaces, it is necessary to assume that every part of the surfaces of contact is uniformly rough ; that the solid parts which are imperfectly rigid, and the cords which are imperfectly flexible, are constituted throughout their entire dimensions of a uniform material ; so that...
Σελίδα 268 - Jixed pulley. Since the tension of the cord is uniform throughout its length, it follows, that in this machine the power and weight are equal. For the weight stretches that part of the cord which is between the weight and pulley, and the power stretches that part between the power and the pulley. And since the tension throughout the whole length is the same, the weight must be equal to the power. Hence it appears, that no mechanical advantage is gained by this machine.