CHAPTER V 

 FLUID METHODS OF SURVEYING BOREHOLES 



Introductory Note. — The outline of a fluid in a container 

 was the first means by which the deflection of boreholes was 

 surveyed in a systematic manner; it is still the most 

 widely employed method. 



Present-day plumbing devices are, so far as demands of 

 reliability can go, very highly complicated, sensitive to 

 injuries, costly and bothersome and also time absorbing 

 in their application. Many of them also require numerous 

 auxiliary appliances, e.g., special rods. On the other 

 hand, the fluid method which we shall describe is cheap, 

 simple in construction and needs less special accessory tools 

 and thereby is for most purposes satisfactory and reliable. 

 The fluid used may be wax, gelatine, hydrofluoric acid, 

 copper sulphate, paraffin or any other substance likely to 

 leave the outline of its surface on the tube container. 

 It depends on the fact that the fluid surface in hollow 

 vessels is always horizontal, independent of what position 

 the vessel takes up. If, therefore, the position of the sur- 

 face is continually known, we may draw exact conclusions 

 as to the position of the vessel at any time. We can fix 

 this surface position by having a glass flask as the hollow 

 vessel and using dilute hydrofluoric acid which has the 

 property of etching the glass. The flask about half full 

 of acid shows the surface in the inclined position as a 

 clear visible ellipse. The action of the acid on the flask 

 walls can be accelerated or retarded by altering the strength 

 of the acid solution. 



In the older methods a short bottle, as in Fig. 47, was 

 suitably enclosed in a protecting cover, half filled with fluid 

 and let down into the hole. In the case of an etching acid, 

 hke HF, the etching action of the fluid on the glass walls 



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