*INVENTIONAL GEOMETRY.*

INVENTIONAL GEOMETRY. |

PRINCIPAL OF THE YONKERS HIGH-SCHOOL.

INVENTIONAL geometry is the name given to a series of carefully graded problems, thought out and arranged by that able mathematical teacher, William George Spencer, the father of the distinguished philosopher.

The little book was published in this country in 1876.^{[1]} An appreciative review in the New York "Evening Post" led the writer to procure a copy, and then to set to work to solve the

simple problems in the order given—the purpose being to form an impartial judgment of the value of the book for school use. A hundred or more problems were wrought, with increasing interest; and then, to make a further test, the book was given separately to a number of pupils, both girls and boys, each being

asked to work as many problems as he could. In each instance the pupil became interested in the work, and wished to continue. The remark of one girl was especially significant. "It's so different from ordinary study," she said; "there's something about it that leads me on."

A class was formed after these tests, and a few months' work

- ↑ New York, D. Appleton & Co., 1876.