The “Terrella”

Abstract

THE name “Terrella” appears to have been first used towards the end of the sixteenth century to describe a sphere of loadstone used as a miniature replica of the earth for the study of terrestrial magnetism. Seventeenth century writers mention terrellas fairly frequently but there are not many descriptions of particular specimens, and although considerable numbers must have been in use during the seventeenth century, very few indeed appear to have survived. Rounded loadstones had been used from very early days. Peregrinus, for example, in the thirteenth century, mentions a method of making them and of finding the poles, but he does not give any particular scientific use to which they could be turned.