Recreations in Mathematics and Natural Philosophy ...

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Página 210 - The number of days in each month may be easily remembered by committing the following lines : — « Thirty days hath September, April, June, and November ; All the rest have thirty-one, Except the second month alone, Which has but twenty-eight, in fine, Till leap year gives it twenty-nine.
Página 117 - One place also is higher than another, or out of level with it, when it is farther from the centre of the earth ; and a line equally distant from that centre in all its parts, is called the line of true level.
Página 111 - But since the mean synodic motion of the moon is at the rate of 30" per minute, it follows that the duration of a total solar eclipse can never exceed four minutes.
Página 477 - ... placed in the water, the lead by its gravity will make the aperture tend directly downwards, and keep in a perpendicular direction the cylinder, to which fire must have been previously applied. To ascertain whether the lead, which has been added to the globe, renders its weight equal to that of an equal volume of water, rub the globe over with pitch or grease, and make a trial, by placing it in the water. The composition with which the globe must be loaded is as follows ; to a pound of grained...
Página 446 - It is evident there must be at least three rods, pierced in proportion to the diminution of the piercer, in order that the powder which is rammed in by means of a mallet, may be uniformly packed throughout the whole length of the rocket. It may be easily perceived, also, that these rods ought to be made of some very hard wood, to resist the strokes of the mallet. In loading rockets it is more convenient not to employ a piercer. When loaded on a nipple, without a piercer, by means of one massy tod,...
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Página 456 - At the moment when the powder begins to inflame, its expansion produces a torrent of elastic fluid, which acts in every direction ; that is, against the air which opposes its escape from the cartridge, and against the upper part of the rocket ; but the resistance of the air is more considerable than the weight of the rocket, on account of the extreme rapidity with which the elastic fluid issues through the neck of the rocket to throw itself downwards, and therefore the rocket ascends by the excess...
Página 447 - These boles serve to form a communication between the body of the rocket and the vacuity at the extremity of the cartridge, or that part which has been left empty. In small rockets this vacuity is filled with granulated powder, which serves to let them off: they are then covered with paper, and pinched in the same manner as at the other extremity. But in other rockets, the pot containing stars, serpents, and running rockets, is adapted to it, as will be shown hereafter.
Página 443 - Rockets may be regarded as the grand basis of all pyrotechnical exhibitions, which are little more than modifications of their form, and of the materials of which they usually consist. A rocket is a cartridge or case made of stiff paper, which being filled in part with gunpowder, saltpetre, and charcoal, rises of itself into the air when fire is applied to it. There are three sorts of rockets : small ones, the...
Página 480 - ... it ought to be put into a large iron mortar, and to be loaded with a quantity of powder proportioned to the weight of the globe. This small mortar must be of light wood, or of paper pasted together, and rolled up in the form of a cylinder, or truncated cone, the bottom excepted ; which, as already said, must be of wood. The chamber for the powder...