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167. oldal - The whole problem is confined within these limits, viz. To make a surface support a given weight by the application of power to the resistance of air.
168. oldal - I shall therefore take 23.6 feet as somewhat approaching the truth. Having ascertained this point, had our tables of angular resistance been complete, the size of the surface necessary for any given weight would easily have been determined. Theory, which gives the resistance of a surface opposed to the same current in different angles, to be as the squares of the sine of the angle of incidence, is of no use in this case ; as it appears from the experiments of the French Academy, that in acute angles,...
171. oldal - ... diminished, and consequently the propelling force, in the same ratio. In practice, the extra resistance of the car and other parts of the machine, which consume a considerable portion of power, will regulate the limits to which this principle, which is the true basis of aerial navigation, can be carried; and the perfect ease with which some birds are suspended in long horizontal flights, without one waft of their wings, encourages the idea, that a slight power only is necessary.
87. oldal - A gazometer, containing seven hundred -cubical feet of gas, weighs about twenty hundred weight, and costs about two pounds ten shillings the hundred weight. The whole of an apparatus complete, capable of supporting forty lamps for four hours, each lamp affording light equal to ten candles of eight in the pound, will cost about two hundred and fifty pounds. Each lamp consumes six cubical feet of gas per hour.
388. oldal - Lecture ; an Account of some new analytical Researches on the Nature of certain Bodies, particularly the Alkalies, Phosphorus, Sulphur, Carbonaceous Matter, and the Acids hitherto undecompounded ; with some general Observations on Chemical Theory.
167. oldal - Let ab be a section of the plane of both wings opposing the horizontal current of air (created by its own motion), which may be represented by the line cd, and is the measure of the velocity of the bird. The angle bdc can be increased at the will of the bird, and to preserve a perfectly horizontal path, without the wing being waved, must continually be increased in a complete ratio (useless at present to enter into) till the motion is stopped altogether; but at one given time the position of the...
13. oldal - VOLTAIC electricity, a dark coloured inflammable substance separating from it on the negative surface, In the course of the spring and summer, I made many attempts to collect quantities of this substance for minute examination. When boracic acid, moistened with water, was exposed between two surfaces of platina, acted on by the full power of the battery of five hundred, an olive-brown matter immediately began to form on the negative surface, which gradually increased in thickness, and at last appeared...
169. oldal - ... edge. This may or may not be the true theory, but it appears to me to be the most probable account of a phenomenon, which the flight of birds proves to exist. Six degrees was the most acute angle, the resistance of which was determined by the valuable experiments of the French Academy; and it gave T% of the resistance, which the same surface would have received from the same current when perpendicular to itself.
112. oldal - ... large cavern near Torquay in Devonshire, commonly known by the appellation of Kent's-hole, and where both species are usually observed in considerable abundance clinging to the vaulted roof of the interior apartments. This vast cavern was explored with a view to obtain whatever species of Vespertilio might inhabit it, and with expectation of procuring specimens of V. Barbastellus, and possibly some new species, having been informed the cave abounded in number and variety. Strange, however, as...
164. oldal - I feel perfectly confident, however, that this noble art will soon be brought home to man's general convenience, and that we shall be able to transport ourselves and families, and their goods and chattels, more securely by air than by water, and with a velocity of from 20 to 100 miles per hour.