. Deep borehole surveys and problems. Boring. 162 DEEP BOREHOLE SURVEYS AND PROBLEMS epoch in the evolution of borehole deflection apparatus; it was the impetus to many later designs and constructions. It conquered the continuous record problem, if however crudely, successfully. We may mark from its inception the rapid evolution of new methods which began in the first decade of this century. Its chief drawbacks are: 1. It is costly and complicated to make. 2. It is heavy though easy to manipulate. 3. Its mechanism and tubes limit the diameters for which it can be Firsi- Measuremenfwi
. Deep borehole surveys and problems. Boring. 162 DEEP BOREHOLE SURVEYS AND PROBLEMS epoch in the evolution of borehole deflection apparatus; it was the impetus to many later designs and constructions. It conquered the continuous record problem, if however crudely, successfully. We may mark from its inception the rapid evolution of new methods which began in the first decade of this century. Its chief drawbacks are: 1. It is costly and complicated to make. 2. It is heavy though easy to manipulate. 3. Its mechanism and tubes limit the diameters for which it can be Firsi- Measuremenfwifh Apparatus Second " Normal ]nsirumeniail Survey Fig. 101.—Checked survey by Erlinghagen's method. 4. Pin-pricking devices are crude and likely to cause confusion in reading. 5. Moisture is likely to injure the apparatus and cable. Thurmann's Apparatus.—This apparatus is built on the proportionality principle, the basis of the lead-basket plumbing method, but it greatly extends the limits of applicabihty of that principle. H. Thurmann, Sr., of Halle obtained reliable results with his apparatus, which is a double plumb bob and linked- tube device, at fair depths. The invention^ (Figs. 1 to 9, Plate XI) consists of straight tubes joined by special cruci- form joints movable in all side directions but not rotatable. 1 Organ des Verein der Bohrtechniker, No. 17, p. 190, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Haddock, M. H. (Marshall Henry). New York, McGraw-Hill
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