40 Sphere in cube

41 Cone and frustrum

42 Octagonal prism

43 Square pyramid

44 Square pyramid and frustrum

45 Triangular prism

46 Explodable square prism

47 Explodable sphere

48 Cube and square root blocks

49 Wood shapes (1)

49 Wood shapes (2)

49 Wood shapes (3)

49 Wood shapes (4)

50 Exploded cube

50 Explodable cube

These models were made by W. W. Ross (1834-1906), superintendent of public schools in Fremont, Ohio from 1864 until 1906. Ross's specialty was wooden models that could be dissected to show how the familiar formulas for areas and volumes in plane and solid geometry could be constructed from simpler pieces. He explains their use in a manual entitled 'Mensuration Taught Objectively, with Lessons on Form.' In the introduction to this manual, he says: 'By means of these Dissected Surface Forms and Solids, ... every ordinary operation in the mensuration of surfaces and solids with possibly one exception can be taught objectively and illustratively so that the pupils shall perceive the reasons of the steps from the first, and the operations themselves shall become the permanent property of the reason rather than the uncertain possession of the memory.' Models like Ross's were viewed by critics as inappropriately driving the curriculum away from standard formulas and toward Ross's objective dissection methods.