By the invention of the goniometer which bears his name, he was enabled to measure the angle formed by the faces of a crystal by means of the reflected images of bright objects seen in them.
"Personal Recollections, from Early Life to Old Age, of Mary Somerville"
Mary Somerville
We bought a goniometer, and Dr. Wollaston, who often dined with us, taught Somerville and me how to use it, by measuring the angles of many of our crystals during the evening.
"Personal Recollections, from Early Life to Old Age, of Mary Somerville"
Mary Somerville
Miller not only measured many of the crystals submitted to him, but evidently taught Darwin to use the reflecting goniometer himself with considerable success.
"Darwin and Modern Science"
A.C. Seward and Others