CHAPTER III.

THE MAGNETIC COMPASS AS A PART OF A SURVEYING INSTRUMENT OR

SEPARATELY:--Broad and Edge-bar Needles--Manufacture of the

Needle--Magnetisation--Suspension--Dip and Adjustment--Lifting--

Inclination--Declination--Variation--Correction--Compass-Boxes--

Description of Compasses--Ring Compasses--Trough Compasses--

Prismatic Compasses--Stand--Surveying with Compass--Pocket

Compasses 59

Surveying and Levelling Instruments, Theoretically and Practically Described. For construction, qualities, selection, preservation, adjustments, and uses; with other apparatus and appliances used by civil engineers and surveyors in the field. · 第 3 / 26 章