274 REPORTS ON THE STATE OF SCIENCE, ETC. 



water into the hole during the drilling. The presence of these irregularities 

 throws considerable doubt on the value of the gradient derived from the 

 observations. The site for this bore hole was chosen so that the bore 

 would be entirely in gault as this is one of the most homogeneous and least 

 porous formations. Thus if irregularities are found in the temperature 

 curve even in this specially favourable case it is unlikely that useful measure- 

 ments will often be possible in such shallow holes. The consistency of 

 the measurements shows however that reliable measurements would be 

 possible in dry holes if any can be found. 



Observations of temperature have been made on lo thermo-junctions 

 in a 15-ft. hole at intervals over a period of a year. These observations 

 should yield an excellent value for the diffusivity of gault. Since they refer 

 to a large mass of undisturbed clay they provide a standard for checking 



0-2 0-4 0-6 



"C BELOW TEMPERATURE AT BOTTOM 



Fig. 2. 



laboratory measurements, for if an apparatus will measure the conductivity 

 of gault there is little doubt that it would deal satisfactorily with more con- 

 solidated rocks. A rough reduction of the observations suggests a value 

 of 0-0037 cm^sec"^ for the diffusivity, which combined with a specific 

 heat of 0-39 cal/°c. grm. and a density of 2-00 gives a conductivity of 

 0-0029 cal/cm.°c. sec. To make a rigorous reduction involves a great deal 

 of arithmetical labour, but it is hoped eventually to carry out the work. 



3. Temperature Measurements in Bore Holes. — The Anglo-Iranian Oil Co. 

 very kindly allowed specimens to be collected and temperatures to be 

 measured in their bore at Kingsclere. As this bore had been made by 

 rotary drilling with a continuous circulation of mud it was necessary to leave 

 it for some days for the lower part to get into temperature equilibrium 

 (see § 4). After the bore had been standing for three days an attempt was 

 made to lower two maximum thermometers in a sealed case. It was found 

 to be impossible to get the thermometers more than halfway down the hole 

 owing to an obstruction. Attempts were continued for three days without 

 success. As this work caused great delay and inconvenience to the Anglo- 



