a 101 
of pressure are too small to affect the conclusions. The results are recorded in the 
following table :—. 
TaBLeE IV. 
: | (Feet.) 
Ee { — —-+ =~ = 
40 lbs, —- 47 18 18 | ue Ove 
51 18 18 oe 1} (see Be: below) 
| 56 18 18 | - 1} (see ot below) 
. Hs = | 36 1 
65 18 28 a es 
BOOlbsy = 8 34} 344 70 i 
af eke | Ce 
45 20 20 | ue ; 
1,600 Ibs. = - 85 60 60 | Ne see Bigspy) 
86 60 60 | ee 5 
ec tae tian Uo aR 
1,900 lbs. - = 88 64 64 oy | a 
i 6 184s | B 
a. NS aut S| teh achat 
| 
Vote—In shot 51 the damage to the first mine case was almost entirely along the equatonal weld ; 
in shot 56 the whole damage to the first mine case was along the same weld, which had opened round 
half the circumference of the mive; in both cases, apart from the weld, the damage would have been 
very slight. 
It will be seen that the distance at which a 40-lb. charge just ceases to inflict any 
damage on the mine case is about 30 feet. ‘Taking distances in the ratio of the cube 
root of the weight of explosive, a distance of 126 feet from a 1,600-Ib. charge corre- 
sponds to 37 feet from a 40-lb. charge, so that if the damaging range of a charge is 
proportional to W! the damage should be the same in these two cases; actually, the 
mine case is heavily damaged at 126 feet from a 1,600 lb. charge, while it would 
certainly be quite untouched at 37 feet from a 40-lb. charge. Again, if the damaging 
range is proportional to W', a 1,600-lb. charge at 189 feet should have the same effect 
as a 40-lb. charge at 16 feet ; actually, the big charge at 189 feet causes no damage 
at all, while the damage from a 40-lb. charge at 16 feet would certainly be very heavy. 
It is clear, therefore, that the damaging range is proportional to something between 
W! and W3, and the experiments with 1,9U0-lb. charges show that it is very approxi- 
mately proportional to W'; for it may be inferred from the results in the table that 
a 1,900-lb. charge at 170 or 175 feet would produce the same damage as a 40-lb. 
charge at 26 feet, and on the assumption that the damaging range is proportional to 
W}, a distance of 179 feet from the big charge corresponds to 26 feet from the small 
charge. On the same assumption the same damage should result from a 300-lb. 
charge at 71 feet, which is in good accordance with the observations. 
These results bring out clearly that it is neither maximum pressure nor time- 
integral of pressure that determines this kind of damage, but something inter- 
mediate ; a high maximum pressure is no use if it is not sufficiently sustained to 
deform the structure beyond its power of elastic recovery, and a high time-integral of 
pressure is no use if the pressure is less that the structure is able to resist. The 
O AS 7498 
