. The Canadian field-naturalist. THE CANADIAN FIELD-NATURALIST ^fjiV. VOL. XXXIII. DECEMBER, 1919. No. 6. CHAMPLAIN'S ASTROLABE. By Charles Macnamara, Arnprior, Ontario. The astrolabe was an instrument for measuring the altitude and relative positions of heavenly bodies. It was probably invented by those eminent astron- omers of antiquity, the Chaldeans; at any rate it was well known to the Greeks and Orientals long before Christ. Essentially it consisted cf a grrdu- ated circle, across the diameter of which was a moveable bar, pivoted at the centre. In use the instrument was hung plumb, and t
. The Canadian field-naturalist. THE CANADIAN FIELD-NATURALIST ^fjiV. VOL. XXXIII. DECEMBER, 1919. No. 6. CHAMPLAIN'S ASTROLABE. By Charles Macnamara, Arnprior, Ontario. The astrolabe was an instrument for measuring the altitude and relative positions of heavenly bodies. It was probably invented by those eminent astron- omers of antiquity, the Chaldeans; at any rate it was well known to the Greeks and Orientals long before Christ. Essentially it consisted cf a grrdu- ated circle, across the diameter of which was a moveable bar, pivoted at the centre. In use the instrument was hung plumb, and the body whose altitude it was desired to ascertain, was sighted along the bar, the angle above the horizon being read on a scale at the edge of the circle. The name of the instrument, derived from the Greek, may be translated as "; The astrolabe gradually developed into two dif- ferent types: a large stationary spherical apparatus that was the chief instrument in observatories even into the 17th century, and a small circular model that could be conveniently carried by travellers. This portable type was often richly ornamented, and engraved with elaborate graduations and scales, but about 1480 a simple form was designed for the use of mariners, and it was apparently this model that Columbus used on his voyages of discovery. It proved, however, an awkward instrument on a pitch- ing vessel, and shipmen generally seem to have pre- ferred another device known as the cross-staff. Nevertheless, the astrolabe continued in use until well into the 18th century, when it was displaced by the quadrant. In 1867 an astrolabe was found near Cobden, Ontario, on the old portage route which cuts off the great elbow that the Ottawa river makes to the north between its expanses known as Allumettc lake and Lac des Chats; and as first noticed by the late A. J. Russell of Ottawa, in a pamphlet pub- lished in 1879, evidence points strongly to the instru- ment having been lost by Ch
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