06 



ME. W. E. BALDWIN-WISEMAN OX 



[Feb. 1907, 



recorded at each inch of depth below the pressed surface by piezo- 

 meter tubes, projecting radially into the rock-mass and closed at 

 the outer end, the tubes being so arranged that no one tube inter- 

 fered with the now past any other ; and results as shown in the 

 following Table (X) were obtained as the averages of a large 

 number of separate experiments : — 



Table X, showing the Pressure ih lbs. per Square Inch at various 

 Depths from the pressed Surface in similar Thicknesses of Eock. 



i 1 



Surface- Micheldever Chalk. Bradford Oolite. Hard Baresbury Sandstone. 



pressure 



in lbs. 1 











I! 







persq.in. 1 in. 2 in. 



3 in. 



4 in. 



Sin. 1 in. 



2 in. 

 6-3 



Sin. 4 in. 5 in. 1 lin. 

 5-4 4-4 3-6 6-0 



2 in. 3 in. 

 4-9 41 



4 in. 

 2-9 



5 in. 



10... 



9-4 8-8 



8-4 



7-9 



7 7*3 



1-4 



20 ... 



18-9 17-7 



16 8 



15-9 



14-2 14-9 



12-9 



11-1 9-2 7-4 12-0 



9-9 82 



5-8 



2-7 



30 ... 



28-2 26-8 



25-3 



23-8 



21-2 22-4 



197 



169 141 11-2 182 



14-9 12-5 



8-8 



4-1 



40 ... 



37'6 35-2 



33-6 



31-8 



283 30-0 



26-1 



22-6 187 15-0 24-1 



20-0 16-4 



11-7 



5-5 



50 ... 









... 37*5 



32-8 



28-2 233 18-8 30'2 



25-0 20-9 



14-7 



6-8 



60 ... 





... 



... 



... 45-2 



39-7 



34-0 28-2 22-7 36-1 



30-0 25-1 



17-8 



8-2 



70 1 ... 



... 





... 52-8 



46-2 



397 32-9 26-3 424 



35-2 294 



20-7 



9-7 



Table XI, showing average Loss of Unit-Pressure per Inch of Depth. 



Distance in inches 

 from surface 

 under pressure. 



Loss of unit-pressure per inch 



of depth in 



Micheldever 

 Chalk. 



Bradford 

 Oolite. 



Hard Baresbury ( 

 Sandstone. 



2 



0-060 

 0-057 

 0-053 

 0-052 

 0-059 



0-250 

 0-170 

 0-146 

 0-133 

 0-125 



! 

 0-396 

 0-250 

 0-194 

 0-176 

 0-173 



3 



4 



5 





If the difference between the surface-pressure and the pressures 

 at the several depths be divided by the respective depths beneath 

 the surface and by the corresponding surface-pressure, as shown in 

 the preceding Table (XI), one has a directly-comparable rate of loss 

 of pressure for each stone ; and it will be observed that there is a con- 

 siderable difference in the rate of variation of pressure in the chalk 

 and in the sandstone, the sides of the cone of depletion having a 

 steeper rise in the immediate vicinity of the centre of disturbance 

 for the chalk than for the sandstone. Curves which are plotted 

 from data such as those embodied in the preceding table have a close 

 resemblance to the outline of those cones of depletion that have 



