out of what, in some shape or other, had been before men’s eyes from the beginning of the world, his powerful genius extracted the most important results.  The invention of pendulum clocks took place about the middle of the seventeenth century; and the honour of the discovery is disputed between Galileo and Huygens.  Becher contends for Galileo, and states that one Trifler made the first pendulum clock at Florence, under the direction of Galileo Galilei, and that a model of it was sent to Holland.  The Accademia del Cimento also expressly declared, that the application of the pendulum to the movement of a clock, was first proposed by Galileo, and put in practice by his son, Vincenzo Galileo, in 1649.  Huygens, however, contests the priority, and made a pendulum clock before 1658; and he insists, that if ever Galileo had entertained such an idea, he never brought it to perfection.  Beckmann says the first pendulum clock made in England, was constructed in the year 1662, by one Tromantil, a Dutchman; but Grignon affirms that the first pendulum clock was made in England, by Robert Harris, in 1641, and erected in Inigo Jones’s church of St. Paul, Covent-garden.

Why does the pendulum move faster in proportion as its journey is longer?

Because, in proportion as the arc described is more extended, the steeper are its beginning and ending; and the more rapidly, therefore, the pendulum falls down at first, sweeps along the intermediate space, and stops at last.—­Arnott.

Why is it extremely difficult to ascertain the exact length of the pendulum?

Because of the various expansion of metals, respecting which no two pyrometers agree; the changeable nature of the atmosphere; the uncertainty as to the true level of the sea; the extreme difficulty of measuring accurately the distance between the point of suspension and the centre of oscillation, and even of finding that centre; also the variety of terrestrial attraction, from which cause the motions of the pendulum are also liable to variation, even in the same latitude.  In pursuing his researches, Capt.  Kater discovered that the motions of the pendulum are affected by the nature of the strata over which it vibrates.

Why is the iron rim of a coach wheel heated before putting on?

Because the expansion of the metal occasioned by the heat, facilitates the operation of putting on the iron, while the contraction which follows, brings the joints of the wooden part together; and thus, binding the whole, gives great strength to the wheel.

Why does a bottle of fresh water, corked and let down 30 or 40 feet into the sea, often come up again with the water saltish, although the cork be still in its place?

Because the cork, when far down, is so squeezed as to allow the water to pass in or out by its sides, but on rising, it resumes its former size.

Why do bubbles rise on a cup of tea when a lump of sugar is dropped into it?