Timbuktu
a city of the Sudan, Central Africa, in lat. 17° 37′ N. and lon. 3° 5' W.; 6 miles N. of the Niger at the extreme N. point of its course.
The town is triangular in shape, and at present is less than three miles in circumference, though formerly it was much larger. The wall or rampart which surrounded it was destroyed by invaders in 1826, and has not been rebuilt. The streets are for the most part straight and unpaved, with a gutter in the center.
Most of the houses are of clay, and some are two stories high, a very unusual thing in Negroland. On the outskirts there are a good many conical huts of matting. Of the mosques, two are especially noteworthy from their great size and imposing appearance, viz., that of Sankoré in the N., and the great mosque in the W. angle of the town. The latter is 286 feet long and 212 feet wide. Timbuktu has also two markets. The climate is unhealthy, and the surrounding country being desert, or nearly so, all supplies of food are brought by the Niger from Sandsanding to Kábara, the port of Timbuktu. The manufactures are confined to a little iron work, and to leather bags, pouches, cushions, etc., made by the Tuarick women. The place owes its importance entirely to its commercial situation, which makes it the entrepôt for the trade between the N. and S. of the Sahara. In addition to the Niger there are two main channels by which commerce flows to Timbuktu, viz., the caravan routes from Morocco on the N., and Ghadames on the N.
E. The principal articles of trade are gold in rings, salt, English calico, red cloth, cutlery, looking-glasses, rice, rice, negro corn, kola nuts (a substitute for coffee), ginger, tobacco, dates, and tea.
Timbuktu was founded toward the end of the 11th century, and became known to Europeans in 1373. Pop. (1917), about 16,000.
TIME TIME. Time and space are the two great elements with which the astronomer in the observatory has to deal; consequently a great part of astronomical work, and a great part of the equipment of every observatory, is devoted to the determination of time in various ways and for various purposes.
Measurement of Time. This is accomplished by the joint work of the clock and watchmakers, and of the astronomer who makes observations of the transits of the heavenly bodies across the meridian to determine the necessary daily corrections to these instruments. For no piece of chronometric apparatus, even the best constructed astronomical clock, can begin to approach in regularity of running the motions of the heavenly bodies, especially the rotation time of the earth on its axis, on which most time determinations depend. The principal pieces of apparatus used for keeping time are various forms of clocks and watches. Before the invention of these instruments the measurement of time was very rough, the most accurate being the method of the sundial; but as this was only good in the day time and when the sun was shining, various rougher devices were employed, such as running sand in the hour glass, the water clocks, or clepsydræ, or even a burning candle. The senseless division of the day into two periods (of 12 hours each), which was probably originally brought about by the use of the sun's shadow in the day time and something or nothing else in the night, is one of the relics of barbarism which seems to be the hardest to get rid of. Even the division into 24 hours (instead of decimals of the whole day, as it ought to be) is bad enough, but, on account of the radical change necessary in the construction of all clocks and watches in order to bring this about, it will probably be a long time in coming.
But the small changes necessary in the dials in order that they may read up to 24 hours instead of 12 makes it surprising that there is so much opposition to the proposal of the railroad managers simply to print their time tables with the day divided in that way.
Different Kinds of Time. Two different kinds of time, with different actual lengths of the unit, are in common use mean solar and sidereal. The mean solar day marks the average interval of the return of the sun to the same meridian.
The time marked by the return of the actual sun is not uniform, and is called apparent time. The difference between mean and apparent time is called the equation of time. Mean solar time is that in common use, but the mean solar one called the civil day, or civil time, be- day is used in two different ways; the TIME day is used in two different ways; the one called the civil day, or civil time, be- electric current passes through the clock gins the day at midnight, and is the one and is broken or closed regularly by a near the exact times as possible. An used by the people at large. The other, toothed wheel on the second hand arbor used by astronomers, begins the day at of the clock. Perhaps the best known according to how the matter is viewed. by the Naval Observatory at Washhours. The day begins 12 hours later by the Naval Observatory at Washthan the civil day, or 12 hours earlier, ington. according to how the matter is viewed. four minutes before noon, whenever the Thus at 6 P. M., Jan. 23, the astronomer telegraph companies switch in the loops It is as follows: three calls it Jan. 23 days 6 hours, or Jan. to the observatory, the clock begins to 23 days 18 hours, or Jan. 23.75 days. If Likewise he calls Jan. 24 at 6 A. M. Jan. 23 days 18 hours, or Jan. 23.75 days. If we consider that 23.25 days and 23.75 but if they are to be regarded as parts of the astronomical day is half a day behind; but if they are to be regarded as parts of the 24th day, as they should be just as much as 1850 is regarded as the middle of the 19th and not the 18th century, then the astronomical day is 12 hours ahead of the civil. It is simply a question of interpretation. as above defined is generally called The astronomical time simply "mean time," to distinguish it from either civil time or sidereal time.
Sidereal time is of an entirely distinct length from mean solar, the sidereal day marking the successive transits of the being very nearly equal to the rotation time of the earth on its axis. The sidereal day equals 23 hours 56 minutes 4.090 seconds of mean solar time, and there is one more sidereal day in the year than solar days. The sidereal day is not of absolute uniform length, as the precession of the equinoxes is not absolutely uniform, but the variations in its length are out in decimal places of seconds beyond those given above. Sidereal time is only used in observations by astronomers. transit instruments for the determination All observations with of the right ascensions of the heavenly transit instruments for the determination bodies are recorded by sidereal clocks, and the observation made simply for the mean time clock for the purpose of time distribution are generally made on the nometer, and then the mean time clock is compared with the sidereal afterward nometer, and then the mean time clock to determine its correction.
Time Signal.- Many observatories send out time signals either daily, hourly, or sometimes continuously every second, or every other second, to various parts of the country for the purpose of giving accurate time to all sorts of industries.
They are sent over the telegraph lines, the wires being permanently run into the observatories for the purpose, and the the wires being permanently run into the by a distributing clock which is kept as or send out make-circuit signals every second over the various lines, the minutes being indicated by leaving out the seconds 55, 56, 57, 58, and 59 in each, and the half minutes by leaving out the 29th second of each. The click following such the beginning of a half-minute, and the first following a gap of five seconds india one-second gap then always indicates cates the beginning of a minute, except at the exact noon. Just before this there is a gap of 10 seconds, and then exactly closed for just a whole second, the beat noon the circuit closes and remains in order to make sure that that particuginning of the mark indicating exact lar mark goes through all the telegraph noon. The closing for a whole second is lines, for the particular signal is made to do a great many things at different and it is more important that this particular second be distinctly sent than any of the others. After the break at the close of the noon signal the telegraph companies quickly switch out the loops to the observatory, and the lines immeiately resume their normal work. In the city of Washington this particular noon signal drops a time ball on the top of the State, War, and Navy Department signal drops a time ball on the top of building, and it also automatically corthe State, War, and Navy Department all the clocks in the department buildings of the government, no matter how much they may have gained or lost since the preceding noon.
Local mean time is that indicated by the transits of the sun at any particular Local, Universal and Standard Time.meridian, and of course this differs for places of different longitudes on the surence of longitude between two places is face of the earth. In fact, the differsimply the difference of their local times, and the accurate determination of this difference is one of the most common kinds of astronomical work, especially in the principal observatory of any country.
The operation consists simply in making the most accurate determination possible of the clock-corrections at each observa- The operation consists simply in making the most accurate determination possible TIME other. But if this local time is used as the standard time at every place it causes the greatest confusion to people traveling from one place to another and to the railroads connecting them. England early adopted the time of the Greenwich meridian for the whole country, and likewise France that of Paris. In the United States uniformity was more difficult on account of the great difference of longitude of its different parts. San Francisco time being nearly four hours slower than the local time in the E. part of Maine. But an excellent compromise was brought about in 1883, principally through the influence of the railroads, pushed on by a few scientific men, and it resulted in the present system of standard time throughouut the country.
This is based on Greenwich time, and differs from it at any place by some whole number of hours, the minutes and seconds being the same over the whole country, and exactly the same as those of Greenwich. The E. part of the country uses time five hours slower than that of Greenwich, or Greenwich fivehour time; i. e., when it is standard noon in the E. part of the United States it is 5 P. M. at Greenwich. In the Mississippi valley they use Greenwich six-hour time.
The dividing line is not an arbitrary one, but is settled by the railroads, generally where they find it most convenient to change at the end of divisions of the roads. The Pennsylvania a roads change at Pittsburgh. The cities and towns along the roads adopt the time of the nearest railroad, and no inconvenience results even where the difference of standard from local time is something more than half an hour. The only inconvenience is in cities like Pittsburgh, where two different hours are used by different railroad systems centering there. But the trouble is infinitely less than it was when there were more than 70 different standards of railroad time in the country. Out on the plains they use Greenwich seven-hour time, and on the Pacific slope Greenwich eight-hour time.
These four standards are commonly called the Eastern, Central, Mountain, and Pacific time, respectively. See See DAY- LIGHT SAVING.
While the above is not an ideal system, it is about the best that can be used at the present time. If the people at large can ever be educated up to the standard of dissociating entirely 12 o'clock from noon, then we can adopt a universal time for all parts of the earth.
This is already done by many scientific men, especially astronomers, meteorologists, and those having any thing to do with terrestrial magnetism, it being nec- TIMOR essary in all these matters to have a common universal time for use, and Greenwich time, either mean or civil, as defined above, is almost universally adopted for these purposes. Such a time is also a necessity in international telegraphic communication, and, once adopted, would be found of universal convenience. Its introduction would come about much easier if at the same time the 12 or 24-hour division of the day could be abandoned, and the decimal division of a universal day come into general use. This, however, involves the abandonment of all existing time pieces and the purchase of new ones showing the decimal division of the day, and as this involves a large financial outlay it will be very difficult of introduction.