Recreations in Mathematics and Natural Philosophy ...

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Էջ 168 - From the foregoing statements it may be safely inferred that " the mean height of the barometer at the level of the sea being the same in every part of the globe...
Էջ 434 - ... sides, forming a multitude of ramifications heaped one upon the other, which will sometimes pass over the edge of the vessel, and extend themselves on the outside, with all the appearance of a plant. If any of the liquor...
Էջ 187 - For this purpose, circular and horizontal indentations are cut out quite around it, and at proper distances, according to the thickness to be given to the millstones. Wedges of willow, dried in an oven, are then driven into the indentations, by means of a mallet. When the wedges have sunk to a proper depth, they are moistened, or exposed to the humidity of the night, and next morning the different pieces are found separated from each other. Such is the process which, according to M. de Mairan, is...
Էջ 65 - ... will have a very sensible motion; so that the moveable extremity of the small bar cannot pass over the hundredth or thousandth part of a line, without a point of the circumference of the last wheel passing over several inches. If this circumference then have teeth fitted into a pinion, to which an index is...
Էջ 183 - WHEN philosophers saw water rise in a capillary tube, above the level of that in which it was immersed, or above that at which it stood in a wider tube^ with which' it formed an inverted siphon, they were induced to conjecture the possibility of a perpetual motion ; for if the water, said they, rises to the height of an inch above that level, let us interrupt its ascent, by making the tube only three quarters of an inch in height : the water will then rise above the orifice, and falling down the...
Էջ 188 - Mairan ; but in our opinion, the answer which he gives to it is very unsatisfactory. It appears to us to be the effect of the attraction by which the water is made to rise in the exceedingly narrow capillary tubes with which the wood is filled Let us suppose the diameter of one of these tubes to be only the hundredth part of a line ; let us suppose also, that the inclination of the sides is one second, and that the force with which the water tends to introduce itself into the tube, is the fourth...
Էջ 432 - ... the metallic part of the cobalt, which communicates to the zaffre its blue colour ; then dilute the solution, which is very acrid, with common. Water. If you write with this liquor on paper, the characters will be invisible ; but when exposed to a sufficient degree of heat, they will become green. When the paper has cooled they will disappear. It must however be observed, that if the paper be heated too much, they will not disappear at all. REMARK.— -With this kind of ink some very ingenious...
Էջ 438 - BEND any thin coin, and put it into half a walnutshell ; place the shell on a little sand, to keep it steady. Then fill the shell, with a mixture made of three parts of very dry pounded nitre, one part of flowers of sulphur, and a little saw-dust well sifted. If you then set light to the mixture, you will find, when it is melted, that the metal will also be melted...
Էջ 150 - But a considerable part of this water, perhaps three fourths, immediately runs off: so that no more than 405000 forces its way through the earth and sandy soil, till it meets with a bed of clay at the depth of two or three feet, from which it flows to the mouth of the fountain, and feeds it. If 405000 therefore be divided by 365, the quotient will be 1100 cubic feet of water, which it ought to furnish daily, or about 38500 French pints; which makes about 1600 pints per hour, or 27 pints per minute.
Էջ 203 - To melt lead in a piece of paper. Wrap up a very smooth ball of lead in a piece of paper, taking care that there be no wrinkles in it, and that it be every where in contact with the ball ; if it be held, in this state, over the flame of a taper, the lead will be melted without the paper being burnt. The lead, indeed, when once fused, will not fail in a short time to pierce the paper, and to run through.