FLUID METHODS OF SURVEYING BOREHOLES 103 



The Phials or Clinostats. — The construction of these 

 can be readily seen in Fig. 52, which shows the position 

 of the magnets and plummets while the phials are hot and 

 vertical. If inclined, say at an angle of 45 deg., the plum- 

 met rods, still vertical, would occupy the then uppermost 

 part of their containing spheres, while the magnets, still 

 horizontal and free, would rest vertically upon the pivots 

 m the then lowest portion of their containing spheres. 

 The clinostat is a true cylinder of glass fitting in the brass 

 guide tube. At the lower end, the phial has a short 

 neck and a bulb, and within the latter a magnetic needle 

 is held upright on its pivot by a glass float, in every position 

 of the phial. This allows the needle, which is fixed upon 

 its ^'peg," to assume the meridian freely at all times 

 without touching the sides of the hollow bulb. Passed 

 through an airtight cork and screw capsule at the upper 

 end is a small glass tube terminating in another bulb 

 above, and with its open lower end inserted in a cork 

 which enters the lower neck of the phial. This prevents 

 the escape of the needle and float already mentioned as 

 occupying the lower bulb. The upper bulb contains 

 a delicate plummet rod of glass consisting of a fine rod 

 terminating in a plumb of solid glass below and in a small 

 bulbous float of hollow glass above. It is very carefully 

 adjusted to the specific gravity of the solidifying fluid 

 in which it, like the magnet, is immersed. Its poise is so 

 adjusted as to insure that the rod or shaft shall be truly 

 in the perpendicular line, whatever the position of the phial 

 and bulb may be. While fluid, the contents of each phial 

 (which completely fill both upper and lower hulhs) permit 

 the plummet to hang freely vertical in the center of its chamber, 

 and allow the needle in the lower bulb to assume the 

 magnetic meridian exactly. When the phial is at rest in 

 any position from vertical to horizontal, and pointing 

 in any bearing as it inclines, the contents sohdify on cooling, 

 and by this means hold fast the indicating plummet and 

 magnet embedding them in a solid transparent substance. 

 The phial then contains within itself an automatic registra- 



