Note 45 — Chapter X · SIR MARTIN FROBISHER

Chancellor had used the cross-staff. Frobisher had been supplied with a similar instrument called a “ballestilla,” which he used in preference to the astrolabe, both being among the instruments and charts bought at a cost of £47. 0s. 8d. of Humphrey Cole and others. The cross-staff was described by Gemma Frisius, and Gunter’s was a yard long, with a cross-piece of 26½ inches. The staff, which was of wood, was graduated, and the cross-piece was moved along it until, looking through the sight near the eye, the two objects were covered of which the angle was to be measured. In observing for the latitude the two objects were the sun and the horizon, the angle giving the altitude.