Rudiments of Natural Philosophy and Astronomy: Designed for the Younger Classes in Academies, and for Common Schools

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S. Babcock, 1844 - Astronomy - 288 pages
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Page 272 - It appears once in eleven months, remains at its greatest brightness about a fortnight, being then, on some occasions, equal to a star of the second magnitude. It then decreases about three months, until it becomes completely invisible, and remains so about five months, when it again becomes visible, and continues increasing during the remaining three months of its period. Another very remarkable variable star is Algol...
Page 92 - Barometer. The barometer is an instrument for measuring the pressure of the atmosphere.
Page 225 - Eclipses of the sun are more frequent than those of the moon. Yet lunar eclipses being visible to every part of the terrestrial hemisphere opposite to the sun, while those of the sun...
Page 212 - evidence of things not seen," in the fulness of Divine grace ; and was profound on this, the greatest concern of human life, while unable even to comprehend how the " inclination of the earth's axis to the plane of its orbit" could be the cause of the change of the seasons.
Page 225 - In any year, the number of eclipses of both luminaries cannot be less than two, nor more than seven. The most usual number is four, and it is very rare to have more than six.
Page 180 - Fig. 1, the angle contained between the two radii, CA and CB, that is, the angle ACB, is measured by the arc A B.
Page 277 - ... suppose that we can enter into them to any but a very small degree. They doubtless go immeasurably beyond our mode of understanding or conceiving them. But to a certain extent we can go. We can go so far as to see that they are Ends and Purposes. It is not a vain presumption in us to suppose that we know that the eye was made for seeing and the ear for hearing.
Page 93 - ... inches, measured from the surface of the fluid in the cup, and not much lower. The mercury is sustained in the tube by the pressure of the atmosphere on the surface of the fluid in the cup. Such a tube and cup, so filled, would in fact be a barometer ; and if a...
Page 189 - The tropics are the parallels of latitude which pass through the solstices. The northern tropic is called the tropic of Cancer ; the southern, the tropic of Capricorn. The polar circles are the parallels of latitude that pass through the poles of the ecliptic, at the distance of twenty-three and a half degrees from the poles of the earth.
Page 171 - By means of this instrument, the eels in vinegar, which are usually so small as to be invisible to the naked eye...

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