Part 23 (1/2)

CHAPTER XII

SPECTACLES, MARINER'S COMPass, BAROMETER, THERMOMETER, WATCHES, CLOCKS, TELESCOPE, MICROSCOPE, GUNPOWDER, STEAM ENGINE, AND ELECTRO-MAGNETIC TELEGRAPH

When were Spectacles invented, and as their inventor?

It is supposed that they were first known about the thirteenth century, and invented by a monk of Pisa, in Italy, named Alexander de Spina Spectacles are colass set in a fralasses called?

Lenses They are either convex or concave, according to the kind of sight requiring thes at a distance, froht converging so as to meet in the centre, require convex lenses

People who can only distinguish objects when viewed closely, fro too convex, require concave lenses to counteract it by spreading the rays, and thus rendering vision distinct

_Convex_, rising outwardly in a circular form; opposite to concave

_Concave_, hollow; round, but hollow, as the inner curve of an arch, &c

_Converging_, tending to one point fro

What is the Mariner's Compass?

A most useful and iuides his shi+p on the sea, and steers his way to the place of his destination The inventor of the Mariner's Compass is not known, nor the exact tiation about the middle of the thirteenth century, and has been in use more than five hundred years The Chinese are said to have been acquainted with it much earlier, but no reliance can be placed on their dates The power of the loadstone to attract iron was known to the ancient Egyptians, but it was not applied to any practical purpose

_Navigator_, one who guides a shi+p

_Steer_, to direct or guide a vessel in its course

_Destination_, the place to which a person is bound

_Practical_, capable of practice, not merely speculative

What is the Loadstone?

An ore of iron which possesses the peculiar property of attracting iron, na it in contact with its ownit firmly attached by its oer of attraction A piece of loadstone drawn several ti a needle, or a snet; if this netized needle is carefully balanced, it will turn round of itself, till its end points towards the North Theiron, and of co this power to another piece of iron or steel, similar to that of the loadstone itself

_Contact_, touch

_Magnetized_, rendered netic