Mensuration
2 of the 7 encyclopedias on this shelf carry an entry for Mensuration. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
the art of measuring. Properly speaking mensuration is an application of geometry. Some of the common principles are the following: The area of a triangle is equal to half the product of its base by its altitude. The area of a square, rectangle, or parallelogram, is equal to the product of the base and altitude. The area of a trapezoid is equal to half the product of the sum of the two parallel sides by the altitude. To find the circumference of a circle, multiply the diameter by 3.1416. To find the diameter of a circle, divide the circumference by 3.1416. To find the area of a circle, multiply the square of the radius by 3.1416. To find the surface of a sphere, multiply the square of the diameter by 3.1416. To find the volume or contents of a sphere, multiply the surface by the diameter, and divide the product by 6. To find the volume or contents of a cylinder, multiply the area of the base by the altitude. To find the volume or contents of a pyramid, multiply the area of the base by the altitude, and divide the product by 3. To find the volume or contents of a cone, multiply the area of the base by the altitude, and divide the product by 3.
Collier's New Encyclopedia (1921)
that branch of applied geometry which gives the rules for finding the lengths of lines, the areas of surfaces, and the volumes of solids. In medicine the term denotes a means for exploring the state of the thoracic and other cavities. MENTAL DEFECTIVES. See IN- SANITY.