Constellation, or Sign. A collection of stars. Astronomers have imagined pictures drawn in the heavens, so as to embrace a number of contiguous stars, and have named the group after the animal, or other article supposed to be drawn; an individual star is generally designated by its fancied location; as upon the ear of Leo, the Lion, &c.
Convergent Rays, are those which approach each other, so as eventually to meet in the same point.
Crystals. Bodies of a regular form, having flat surfaces, and well defined angles. Nitre, and other salts, are familiar examples. Many masses of matter, are composed of crystals too minute to be discerned without glasses.
Curvilinear, consisting of a line which is not straight, as a portion of a circle, of an oval, or any curved line.
Cylinder. A body in the form of a roller, having flat circular ends, and being of equal diameter throughout.
Degree. If a circle of any size be divided into 360 equal parts, each of these parts is called a degree. One quarter of a circle contains ninety degrees; one twelfth of a circle, thirty degrees. The actual length of a degree, must depend upon the size of the circle. A degree upon the equator, upon a meridian, or any great circle of the earth, is equal to 691/2 miles.
Straight lines are sometimes divided into equal parts, called degrees; but these divisions are arbitrary, bearing no relationship to the degrees upon a circle.
Density. Closeness of texture. When two bodies are equal in bulk, that which weighs the most, has the greatest density.
Diagonal. A line drawn so as to connect two remote angles of a square, or other four-sided figure.
Dilatation. The act of increasing in size. Bodies in general, dilate when heated, and contract by cooling.