Keywords: Pocket box circle Galbraith.png en Pocket box-circle navigational instrument invented by mathematician William Galbraith From Arcana of Science 1838 http //books google co uk/books id mLAWAQAAIAAJ pg PA60 img 1 zoom 3 hl en sig ACfU3U15rlvctC0xB3OnWEYl9MxpQxADuw ci 207 2C298 2C607 2C483 edge 0 Google Books Unknown artist 1838 PD-old 1838 engravings Scientific instruments |