T38 TIDES Ham Henry, Aug. 3. In the summer of 1758 Gen. Abercrombie took the command of an expedition for the reduction of Fort Carillon, crossed Lake George with 15,000 men, and on July 8 attempted to take the fort by storm, but was repulsed with a loss of 2,000 men. In 1759 Gen. Amherst at the head of 12,000 men invested Ticonderoga, and the French, not having a sufficient force to hold it, dis- mantled and abandoned it, July 30 ; and soon after Crown Point was also abandoned. The English government then greatly enlarged and strengthened the two fortresses. The fort and field works of Ticonderoga extended over an area of several miles. After the cession of Canada in 1763, the fort was allowed to fall into partial decay, and was held by a small force. Upon the receipt of the news of the battle of Lexington, Col. Ethan Allen surprised the fort, May 10, 1775, and cap- tured the garrison of 50 men and the artil- lery and munitions of war in the fort. (See ALLEX, ETHAN.) The centennial of this event was celebrated in the town on May 10, 1875. In 1776, after an engagement between the British and Americans, the latter were com- pelled to take refuge under the guns of Fort Ticonderoga. On June 30, 1777, Burgoyne in- vested the fort, and on July 4 erected a bat- tery on Sugarloaf hill (now Mt. Defiance), which completely commanded it and com- pelled the garrison to evacuate it the next night, sending their stores and munitions to Skenesborough (now Whitehall), and escaping themselves into Vermont. In September of the same year Gen. Lincoln made an attack upon the works, took Mts. Hope and Defiance, released 100 American prisoners, and took 293 of the enemy, an armed sloop, several gun boats, and more than 200 bateaux, but did not capture the fort. After the surrender of Bur- goyne the fort was dismantled, and the garri- son retreated down Lake Champlain ; some of them were captured by Capt. Ebenezer Allen. In 1780 Gen. Haldeman with a company of British soldiers advanced to Ticonderoga and occupied it for some time ; and from this point Major Carleton made a diversion against Forts Anne and George, in favor of Sir John John- son. After the war the fort fell into ruins; portions of the walls are still standing. There is a history of Ticonderoga by the Rev. Joseph Cook (Keeseville, N. Y., 1858). TIDES, the alternate rising and falling of the waters of the ocean, which is to be observed on all its coasts and estuaries. The rising is designated as the flood, and the highest eleva- tion as high water; the falling is called the ebb, and the lowest depression low water. The duration of high and low water without apparent change of level is known as the stand, and the cessation of the ebb and flood streams or tidal currents is called slack water. The tides of each day occur somewhat later than those of the preceding day, the average retardation from day to day being about 50 minutes. The times of occurrence of high water bear a very close relation to the appear- ance of the moon in certain positions. Thus at New York high water occurs when the moon is about E. S. E. ; at New Castle, on Delaware river, when the moon is nearly S. ; at Baltimore when it is rising or setting. These are rude statements, but they are suffi- ciently accurate for many purposes, and they show at once the close connection between the time of high water and the time of the moon's passage over the meridian. In fact, so com- pletely is this recognized, that, in order to give the time of high water upon any day, it is usu- ally thought sufficient to state the time of high water on the days of new moon and full moon (or "full and change ") when the moon passes the meridian at 12 o'clock nearly. This time is called the establishment of the port. Then to find (roughly) the time of high water on any other day, it is only necessary to add the establishment to the time of the moon's me- ridian passage on that day. There will also be another high water on the same day, pre- . ceding or following that so found by 12h. 26m. nearly. On closer examination it will be found that the interval between the time of the moon's passage over the meridian and the time of high water varies sensibly with the moon's age. At new moon, full moon, first quarter, and third quarter (or rather on the day following each of these phases), the inter- val between the time of the moon's passage and the time of high water is nearly the same ; but from new moon to first quarter, and from full moon to third quarter, the high water oc- curs earlier than would be inferred by using that same interval; and from first quarter to full moon, and from third quarter to new moon, it occurs later than the same interval would give it. The height at high water and the depression at low water are not always the same. On the days following new moon and full moon, high water is higher and low water lower than at any other time ; these are called spring tides. On the days following the first and third quarters, high water is lower and low water higher than at any other time ; these are called neap tides. Thus at New York the rise and fall (that is, the difference in ele- vation between high water and low water) is about 5^ ft. at spring tides, and 3 ft. at neap tides. At Boston this variation is from 11 to 8 ft. There is a sensible difference in height between two successive high waters or low waters, one occurring before noon, the other after noon, and these differences are most per- ceptible when the moon is at her greatest de- clination N. or S., and disappear when she is near the equator. There are other variations of height depending on other circumstances. In a single tide the interval from high water to low water is greater than that from low water to high water; the difference between these intervals is sensibly greater at spring tides than at neap tides. The tidal current in
