During the 18th century the standard textbook for learning geometry was Euclid's Elements of Geometry. This work had been the standard text since Euclid first compiled it in the 3rd century B.C. The models made by Adams illustrate those parts of Euclid that deal with solid geometry (Books XI and XII).
The idea was simple: 3-dimensional models would help students to visualise the geometrical propositions more easily than 2-dimensional images in books. People could learn more readily by handling an object. This selling point of models was given at the time, with one 18th-century author claiming that
"it is almost as necessary as in mechanics, to exhibit the objects, whose qualities are to be taught; and to call in the joint assistance of the hands and eyes." (1)