a. [f. TIDE sb. II. + -AL.]
1. Of, pertaining to, or affected by tides; ebbing and flowing periodically.
Tidal alarm, an audible signal, as a bell or whistle attached to a buoy, operated by the movement of the tides (Cassell’s Encycl. Dict., 1888); tidal crack = TIDE-crack (Cent. Dict., 1891); tidal friction, frictional resistance to the motion of the tide-wave, tending to retard the earth’s rotation; tidal motor, a mechanical motor deriving its power from the movement of tidal waters; tidal river, a river that is affected by the tides for some distance from its mouth; tidal valve, a valve in a sluice, which opens to the pressure of land water and closes under the influence of the incoming tide; tidal wave, see b.
1807. Vancouver, Agric. Devon (1813), 300. Had the lots below … the new Custom House … in Dublin, been left open to the tidal waters, the waters of the Liffy would have preserved a deep channel for their discharge.
1830. Lyell, Princ. Geol., I. 359. Suppose that … the Mediterranean should form a gulf of the great ocean, and that the tidal current should encroach on the shores of Campania.
1853. Herschel, Pop. Lect. Sc., i. § 57 (1873), 45. The tidal action of the sun and moon on … the earth’s crust.
1878. Huxley, Physiogr., i. 2. Up to Teddington … the Thames is a tidal river.
1880. Haughton, Phys. Geog., i. 9. When the length of the day shall have become equal to the length of the year, tidal friction will cease.
1884. F. J. Britten, Watch & Clockm., 256. Tidal Clock … designed … for showing the time of high and low water, the state of the tides at any time of the day.
1911. Encycl. Brit., XXVI. 945/1. Tidal friction then diminishes planetary rotation, increases the satellite’s distance, and diminishes the orbital angular velocity.
b. Tidal wave: the high-water wave caused by the movement of the tide: = tide-wave (TIDE sb. 16 b); erron. an exceptionally large ocean wave caused by an earthquake or other local commotion.
1830. Lyell, Princ. Geol., I. 293. On mathematical principles, the rise of the tidal wave above the mean level of a particular sea must be greater than the fall below it.
1878. Huxley, Physiogr., 2. The tidal wave occupies about two hours in coming up from the Nore to London. Ibid., 188. The terrible devastation wiought by the great tidal wave, which followed the earthquake at Lima.
1899. Daily News, 13 June, 8/2. The tidal wave sweeps round the earth twice in the twenty-four hours; the great wave produced by an earthquake, erroneously described sometimes as a ‘tidal wave,’ has nothing tidal about it, and it is called by scientific men ‘a free wave.’
(b) fig. A great progressive movement or manifestation of feeling, opinion, or the like.
1862. Lilly Waters, in Ladies’ Repository, XXX. 331/1. When the great tidal wave of grief first breaks over us, ’tis as though we sat, a stranger, alone; and in darkness, by some stormy sea.
1884. Boston (Mass.) Traveller, Aug. Van Buren was a candidate again in 1849, but the ‘log-cabin and hard cider’ tidal wave was sweeping over the country.
1888. Bryce, Amer. Commw., III. IV. lxxx. 62. Now and then … there comes a rush of feeling so sudden and tremendous, that the name of Tidal Wave has been invented to describe it.
1895. Scully, Kafir Stories, 50. The repression which he had to exercise … caused tidal waves of passion to roll back on his soul, fraught with destruction to himself and to others.
(c) Phys. The main or primary height of flow in a beat of the pulse.
1896. Allbutt’s Syst. Med., I. 314. Sphygmographic tracings show a lowering in the height of the tidal and dicrotic wave.
2. transf. and fig. That ‘ebbs and flows’; periodic, intermittent; alternating, varying.
Tidal air (Phys.), the air passing in and out of the lungs at each ordinary respiration; tidal breathing (Path.), respiration in which there are pauses alternating with shorter periods of respiratory activity; periodic respiration.
1872. Huxley, Phys., iv. 92. In ordinary breathing 20 to 30 inches of what is conveniently called Tidal air pass in and out.
1876. Geo. Eliot, Dan. Der., IV. xxix. This mood of youthful, elated desperation had a tidal recurrence.
1896. Daily News, 4 May, 3/3. Clerkenwell has … become mixed in population and in its political opinions tidal.
1897. Allbutt’s Syst. Med., IV. 646. Amongst … the results of derangements of the pulmonary circulation must be placed the occurrence of ‘periodic,’ ‘tidal,’ or Cheyne-Stokes breathing.
3. Dependent upon or regulated by the state of the tide or time of high water.
Tidal basin, harbor, a basin or harbor that is accessible or navigable only at high tide; tidal boat, steamer, a vessel the sailings of which depend on the time of the tide; tidal train, a train running in connection with a tidal steamer.
1858. Simmonds, Dict. Trade, Tidal basin, a dock that is filled upon the rising of the tide.
1859. Lewin, Invas. Brit., 27. Boulogne is a tidal harbour,… it can only be entered or quitted at high water.
1859. Reeve, Brittany, ii. 12. The tidal hours of departure of the steam-packet.
1866. W. Collins, Armadale, II. 240. The tidal train … was speeding nearer and nearer to Paris.
1888. Gunter, Mr. Potter, x. The tidal boat’ll be ’ere in twenty minutes.
b. Elliptical for tidal boat or train.
1883. L. Oliphant, Altiora Peto, I. 202. He found himself just in time to take the tidal.
Hence Tidally adv., in a tidal manner; by or in respect of the tides.
1879. G. H. Darwin, in Phil. Trans., CLXXI. 713. On the Secular Changes in the Elements of the Orbit of a Satellite revolving about a Tidally Distorted Planet. Ibid. (1880), CLXXII. 513. In considering the effects of tidal friction the theory has been throughout adopted that the tidally-disturbed body is homogeneous and viscous.
