dred thousand crowns to the person who should solve this celebrated problem; and the States of Holland have proposed a reward for the same purpose.

9. To find at what rate the inhabitants of the earth are carried in a year, day, hour, minute, and second, by the annual motion of the earth.

RULE.

Multiply the earth's distance from the sun by 2, which gives the diameter of the earth's orbit; multiply that by 22, and divide the product by 7; the quotient is the whole extent of the orbit of the earth, and consequently the number of miles we are carried in a year: divide them by 365, the quotient will show the number of miles that we daily pass through; this divided by 24, shows the hourly motion; and that again by 60, produces our motion per minute, which being divided by 60, gives the rate we are carried at per second; or in the time that a pendulum clock beats.

Example. The distance of the earth from the sun, at a mean rate, is given 95,000,000 miles: required at what rate we are carried in a year, day, hour, minute, and second, by the annual motion of the earth?

According to the first rule, which is the most convenient for general use, we find that the vast space passed through in a year, by the earth, is 597,142,857 miles,

in a day 1,636,007 miles, in an hour 68,166 miles, in a minute 1136 miles, and in a second 1856 miles. The uniformity of this rapid motion prevents our feeling or suffering any inconveniency from it.

10. To find at what rate the inhabitants on any part of the earth are carried, by its diurnal motion.

NOTE. The points of the earth at the poles, have no diurnal motion, except that of being turned round in the same place every twenty-four hours.

RULE. Multiply 360, (the circumference of the earth), by the number of miles contained in a degree of the parallel of latitude where the proposed place is situated, (a table of which is given in Chap. IV. Prob. X. for geographical and English miles,) and the product will be the daily motion; divide that product by 24, and the quotient will show the hourly motion; which, if divided by 60, will give the motion per minute.

Example 1. Required at what rate per day, and per hour, the inhabitants at the equator are carried by the diurnal motion of the earth in English miles?

Answer, 25,020 miles per day, and 1042 per hour. 2. At what rate are the inhabitants of London carried per hour, and per minute, by the diurnal

motion of the earth in English miles? the breadth of a degree in that parallel, being about 43 miles. Answer, 648 miles per hour, and 1048 per minute.

CHAP. II.

The rise and progress of geography; definitions of the lines used on the globes, the signs of the zodiac, positions of the sphere, &c.

1. THE RISE AND PROGRESS OF GEOGRAPHY.

THE origin of geography, on which the use of the terrestrial globe is founded, is not of a late date, nor is it likely that a system was formed from the invention of one man: it appears, however, to have been brought to such perfection in the time of Anaximander, the scholar of Thales, a native of Greece, who flourished six hundred years before Christ, that he was able to bring it into regular form, by inventing maps, globes, and the signs of the zodiac.*

Maps and sea-charts were first brought to England by Bartholomew Columbus, in 1489; brother to the celebrated Christe pher Columbus, who discovered America.

Pliny informs us, that Alexander the Great carried geographers with him, to delineate his expeditions in Asia. It was likewise customary among the Romans to delineate their conquests on tables, which were exhibited to the people in their triumphs.

The moderns have, however, added much to the science of geography, by exploring extensive regions unknown to the ancients; of which America, New Holland, and the numberless islands in the Southern Ocean, may be considered as the principal; and have quite exploded the idea of a continent, to any considerable extent, existing towards the south pole.*

The first person that sailed round the earth was Magellan, a native of Portugal, in the service of Spain, who completed his voyage in 1520. The same was performed by Sir Francis Drake, Lord Anson, Captain Cook, &c.

These circumnavigators, not only added information to the system of geography, but likewise a proof of the globular shape of the earth.

That the earth is round, like a ball, is proved by ships having sailed round it; by its shadow, in eclipses of the moon, always being bounded by a circular line; by our seeing the masts of a ship whilst the hull is

* Captain Cook sailed, on the 30th of January, 1774, to the lat. of 71° 10′ S. being then surrounded with islands of ice.

hid by the convexity of the water: as the hills take off no more from the roundness of the earth, in comparison, than grains of dust do from the roundness of a common globe.

The exact shape of the earth was a contested point, of some length, among mathematicians and philosophers; the means that led to its determination were, however, accidental. In the year 1672, Mr. Richer being sent from Paris to Cayenne, in S. America, lat. 4° 56′ N. found that his pendulum clock, which was regulated at Paris to mean time, lost every day nearly three minutes, which is more than could have been produced by the expansion of the pendulum by the hot climate.

This discovery being reported by Mr. Richer, on his return to France, engaged the attention of the greatest philosophers and mathematicians of Europe: it is, however, to the sagacity of Sir Isaac Newton that the world is indebted for the solution of this complex problem, who, from the idea afforded by the observations of Richer, formed an hypothesis, whereby he determined that the earth was in the shape of an oblate spheroid; that is, flattened a little towards the poles, and that its equatorial diameter was nearly 37 miles longer than its polar.

The earth's equatorial diameter is equal to 41,926,356 feet, or 7940,598 miles; and the polar diameter is equal to 41,731,272