Sedimentary Innllings and Development of Major Tertiary Palaeodrainage Systems of South‐Central Australia

A plumb bob assembly includes a hollow conical bob having a conical recess in which is a removable heavy conical insert. The insert has a conical recess in which is a removable conical bob. One or more cylindrical sections are connected successively to the conical bob by detachably engaged threaded nipples and recesses. One or more of the cylindrical members may have conical recesses containing removable other conical bobs. The bobs are of different sizes and different materials.