CONTACT

, the relative state of two things that touch each other, but without cutting or entering; or whose surfaces join to each other without any interstice. |

The contact of curve lines or surfaces, with either straight or curved ones, is only in points; and yet these points have different proportions to one another, as is shewn by Mr. Robartes, in the Philos. Trans. vol. 27 pa. 470; or Abr. vol. 4. pa. 1.

Because few or no surfaces are capable of touching in all points, and the cohesion of bodies is in proportion to their contact, those bodies will adhere fastest together, that are capable of the greatest contact.

Angle of Contact is the opening between a curve line and a tangent to it, particularly the circle and its tangent; as the angle formed at A between BA and AC, at the point of contact A.

It is demonstrated by Euclid, that the line CA standing perpendicular to the radius DA, touches the circle only in one point: and that no other right line can be drawn between the tangent and the circle.

Hence, the angle of contact is less than any rectilinear angle; and the angle of the semi-circle between the radius DA and the arch AB, is greater than any rectilinear acute angle.

This seeming paradox of Euclid has exercised the wits of mathematicians: it was the subject of a long controversy between Peletarius and Clavius; the former of whom maintained that the angle of contact is heterogeneous to a rectilinear one; as a line is to a surface; the latter maintained the contrary.

Dr. Wallis has a formal treatise on the angle of contact, and of the semi-circle; where, with other great mathematicians, he approves of the opinion of Peletarius.

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Entry taken from A Mathematical and Philosophical Dictionary, by Charles Hutton, 1796.

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CONSEQUENT
CONSOLE
CONSONANCE
CONSTELLATIONS
CONSTRUCTION
* CONTACT
CONTENT
CONTIGUITY
CONTIGUOUS
CONTINENT
CONTINUAL Proportionals