An early instrument for measuring altitude of celestial bodies, consisting of a90= graduated arc with a movable radius for measuring angles. 象限仪用来测量天体纬度的一种早期工具,由一个有90度刻度的圆弧和一个用来测量角度的可移动的半径构成
The sun appears to move in an arc across the sky. 太阳看起来在天空以弧线运行。
Arcs more readily than AC welders, with longer arcing. 起弧比交流电容易,电弧加长一倍。
No injuries were reported during the explosion and subsequent arcing that occurred about 9 a.m. at the 19th Street Bay Area Rapid Transit rail station, said Ray Cole, acting manager of system safety.