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Knight's Mechanical Encyclopedia (ed. Knight) 5 1 Browse Search
Thomas Wentworth Higginson, Irene E. Jerome., In a fair country 2 0 Browse Search
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Knight's Mechanical Encyclopedia (ed. Knight), B. (search)
3,040 feet, and carried up with him the necessary means for making scientific observations on the character and properties of the atmosphere at that great hight. This was for many years considered the most remarkable balloon ascent ever made, both in regard to the hight attained and the observations made. The great tenuity of the atmosphere in those elevated regions is said to have affected M. Lussac to such a degree that his system never fully recovered from it. An English aeronaut named Glaisher, it is said, has recently succeeded in reaching the hight of seven miles. He was rendered seriously ill, and was supposed to have burst some bloodvessels. Charles Green introduced the practice of inflating balloons with ordinary illuminating-gas, making his first ascension with this medium on the day of the coronation of George IV., 1820. Illuminating-gas, besides being much cheaper than hydrogen, has the advantage of being more easily retained within the envelope on account of its grea
Knight's Mechanical Encyclopedia (ed. Knight), H. (search)
constantly moist from a cistern fixed on the plate, to which the two are attached. This is the most useful form of hygrometer. The theoretical relation between the indications of the two bulbs and the humidity of the air is rather complex and has given rise to much debate; it is usual to effect the reduction by tables which have been empirically constructed by comparison with the indications of the dew-point instrument of Daniell. The British tables for this purpose were constructed by Glaisher; edition of 1856 preferred. They are based upon a comparison of the simultaneous readings of the wet and dry bulb thermometers, and of Daniell's hygrometer, taken for a series of years in Greenwich Observatory, in Toronto, and in India. The ratio between the two readings is not equal at all degrees of temperature as marked on the dry bulb. When this temperature — the natural, it may be called — is 53° F. the dew-point is as much below the wet bulb as the latter is below 53° F., the tempe<
Knight's Mechanical Encyclopedia (ed. Knight), M. (search)
es upon agate planes, so as to vibrate like the beam of a pair of scales. The buildings appropriated to this purpose at the Greenwich Observatory, England, are built in the form of a cross, of materials from which iron is rigidly excluded. In two arms of the cross are magnetized needles suspended by silk, for observations in declination or variation; and in another arm of the cross is a balanced needle, for observations in inclination or dip. The arrangements were under the control of Mr. Glaisher, and the observations were originally made by himself and two assistants, until Mr. Brooke introduced his adaptation of photography to the purpose of recording observations. By means of mirrors attached to the arms of the magnets, reflected light is east upon highly sensitized photographic paper wound round cylinders moved by clock-work, and the slightest variation of the magnets is registered with the greatest accuracy. See Magnetograph. We shall have occasion to show that the ma
Thomas Wentworth Higginson, Irene E. Jerome., In a fair country, Snow (search)
with the primeval star, especially, seems far and fanciful enough, but there are yet unexplored affinities between light and crystallization: some crystals have a tendency to grow toward the light, and others develop electricity and give out flashes of light during their formation. Slight foundations for scientific fancies, indeed; but slight is all our knowledge. More than a hundred different figures of snow-flakes, all regular and kaleidoscopic, have been drawn by Scoresby, Lowe, and Glaisher, and may be found pictured in the encyclopaedias and elsewhere, ranging from the simplest stellar shapes to the most complicated ramifications. Professor Tyndall, in his delightful book on The Glaciers of the Alps, gives drawings of a few of these snow-blossoms, which he watched falling for hours, the whole air being filled with them, and drifts of several inches being accumulated while he watched. Let us imagine the eye gifted with microscopic power sufficient to enable it to see the mol