CHAPTER IV.

LEVELS:--Methods of Ascertaining--Level Tubes--Manufacture--

Curvature--Sensitiveness--Testing--Reading--Circular Levels--

Surveyors' Levels--Y-Levels--Parallel Plates--Adjustments of

Y-Levels--Suggested Improvements--Dumpy Levels--Tripod Stands--

Adjustment of Dumpy--Collimator--Improvements in Dumpy Levels--

Tribrach Head--Diaphragms--Cushing's Levels--Cooke's Levels--Cheap

Forms of Level--Hand Levels--Reflecting Levels--Water Levels 85

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 4 / 26 章