[ad. L. contact-us (u-stem) touching, contact, f. contact- ppl. stem of contingĕre to touch (each other): cf. F. contact (in Cotgr.).]
1. The state or condition of touching; the mutual relation of two bodies whose external surfaces touch each other. Hence to be or come in (into) contact.
1626. Bacon, Sylva (1628), § 944. As for Loue, the Platonists, (some of them,) goe so farre, as to hold that the Spirit of the Louer, doth passe into the Spirits, of the Person Loued; Which causeth the desire of Returne into the Body, whence it was Emitted: Whereupon followeth that Appetite of Contact, and Coniunction, which is in Louers.
1766. Pennant, Zool. (1776), III. 92. They [Basking Shark] will permit a boat to follow them, without accelerating their motion, till it comes almost within contact; when a harpooneer strikes his weapon into them, as near to the gills as possible.
1799. Med. Jrnl., II. 28. It has been asserted, that the cow-pox cannot be communicated but by contact.
1807–26. S. Cooper, First Lines Surg. (ed. 5), 399. By, which means the edges of the wound in the trachea will be kept in contact.
1849. Ruskin, Sev. Lamps, v. § 10. 145. Bringing it into visual contact with the upright pilasters.
1878. Huxley, Physiogr., 75. So as to avoid contact with air.
1885. Whitaker’s Alm., Eclipses. First contact with the Penumbra, 1 h. 50 m. aft. First contact with the shadow, 2 h. 59 m. aft.
b. with pl.
1718. Quincy, Compl. Disp., 6. The Cohesion in all Bodies must be as the Surfaces and Contacts of their component Parts.
1833. Lamb, Elia, Ser. II. iii. (1865), 260. How he sidled along, keeping clear of all secular contacts.
c. To make or break contact: to complete or interrupt an electric circuit. Cf. contact-breaker, -maker in 6.
c. 1860. Faraday, Forces Nat., vi. 168. If I make contact with the battery, they are attracted at once.
1881. Maxwell, Electr. & Magn., II. 172. If we make contact only for an instant, and then break contact, the two induced currents pass through the galvanometer in … rapid succession.
2. transf. and fig.
To come in contact with: to meet, come across, be brought into practical connection with.
1818. Byron, Ch. Har., IV. cxxv. Though accident, blind contact, and the strong Necessity of loving, have removed Antipathies.
1862. Trollope, Orley F., xiii. 103. Never till now had he come into close contact with crime.
1874. Green, Short Hist., iii. § 4. 127. A new fervour of study sprang up in the West from its contact with the more civilized East.
1889. Illustr. Lond. News, 21 Dec., 782/1. A large baboon … snapping at all it came in contact with.
b. So point of contact.
1862. Lewis, Astron. Ancients, i. § 1. 2. The history of astronomy has numerous points of contact with the general history of mankind.
1883. G. Lloyd, Ebb & Flow, II. 192. They had a point of contact where they least expected it.
3. Math. The touching of a straight line and a curve, of two curves, or of two surfaces; the meeting of two curves (or surfaces) at a point so as to have a common tangent (or tangent plane) at that point; the coincidence of two or more consecutive points on each of two curves.
If two consecutive points on each curve coincide, the curves are said to have contact of the first order; if three, c. of the second order; and so on. Angle of contact: the angle between a curve and its tangent at any point, or the (infinitesimal) angle between two consecutive tangents at that point; also called angle of contingence or of curvature.
1660. Barrow, Euclid, III. xii. If two circles … touch one the other outwardly, the right line AB which joins their centers A, B, shall pass thro’ the point of contact C. Ibid., III. xvi. Any acute angle, to wit, DAE, is greater than the angle of contact DAI.
1840. Lardner, Geom., 187. If one of the cylinders … be rolled upon the other, their line of contact will move parallel to itself.
1884. Williamson, Diff. Calculus (ed. 5), 290–1. The circle which passes through three infinitely near points on a curve is said to have contact of the second order with it. Ibid., 304. The tangent to a curve has a contact of the first order with the curve at its point of contact, and the osculating circle a contact of the second order. Ibid., 306. If the contact be of an even order … the curves cut each other at their point of contact.
4. Geol. Hence contact-bed, -deposit, vein.
1881. Raymond, Gloss. Mining Terms, Contact, the plane between two adjacent bodies of dissimilar rock. A contact-vein is a vein, and a contact-bed is a bed, lying, the former more or less closely, the latter absolutely, along a contact.
5. attrib. a. Chem. Contact action = CATALYSIS. b. Electr. Contact electricity, force, potential: see quot. 1881.
1859. Todd, Cycl. Anat., V. 138/1. To be referred to the class of ‘contact actions.’
1881. Maxwell, Electr. & Magn., I. 337. It appears that when two different metals are in contact there is in general an electromotive force acting from the one to the other, so as to make the potential of the one exceed that of the other by a certain quantity. Ibid., I. 339. This is Volta’s theory of Contact Electricity.
1882. Watts, Dict. Chem., II. 12. Examples of these contact actions are found both in inorganic and in organic chemistry.
1885. Watson & Burbury, Math. Th. Electr. & Magn., 225. This difference of potentials is generally called the electromotive contact forces of the two metals … The metal of higher contact potential.
6. Comb., as contact-breaker, a contrivance for breaking an electric circuit automatically; contact-level, an instrument in which a form of spirit-level is used for the determination of minute differences of length; contact-lever, the lever that moves a contact-level; contact-maker, a contrivance for completing an electric circuit automatically; contact-mine, a mine that explodes by contact; contact-point, the metal point that makes contact in a telegraphic-apparatus.
1838. G. Bird, in Phil. Mag., XII. 18. Description of a magnetic *contact-breaker.
c. 1865. J. Wylde, in Circ. Sc., I. 252/2. The contact between the electro-magnet and the battery is broken by means of any form of contact-breaker.
1886. Pall Mall G., 25 Aug., 14/1. There are in each compartment two incandescent 16-candle power lamps. By the application of a *contact maker, only one is lit at a time. Ibid. (1885), 21 March, 5/1. A *contact mine explodes when struck by a vessel.
1879. G. Prescott, Sp. Telephone, 11. The position of this *contact-point may be adjusted by means of a screw.
1884. Chamb. Jrnl., 25 Oct., 686/1. Iridium has been used … for … contact points for telegraphic apparatus.
