528 
= 4e= 
(c) Magnetic Sensitivity of Cathode Ray Oscillograph, 
Deflection 8¢ = 0,3 4 A(L+ . ) cms, 
where H = strength of magnetic. fietd. 
A = length of magnetic field traversed by the cathode rays. 
and aL = distance from mid-point of magnet to screen, 
4- Capacities of Cable, p.e. Gauges etc. 
k 
(a) Single Core cable in sea (Pattern 1389A as Cc sk 
used with p.e. gauges) 4.50 log = cms. 
1 R 
k = 2.5 for rubber 
Capacity = 0,00%2 ufd. per 100 feet 
(b) pee. gauge (7 inches diameter) capacity 0.00035 yfd. (approx.) 
(c) Oscillograph Deflecting Plates Capacity a few cms, only. 
(d) Aerial Wire (Cs ) d = diameter of wire 
a 109e— eoSe h = height above earth 
= length cms. 
5. Velocity of Explosion Waves* (Smal) Amplitude) 
Vv, = 4756 + 13.8t = 0.12t? feet/second. 
where t is the temperature of the sea in degrees Centigrade and the salinity of the sea is 35%. 
6, Some Properties of Explosives + 
(a) Rates of Detonation. 
—— 
| Explosive Density of Velocity 
Loading metres/sec. 
T.N.T. 
Gun cotton (dry) 
Amato? 40/60 
Mercury Fulminate 
(b) Heat and Gases on Detonation. 
Calories per gram Total gases c.c. 
Explosive water gaseous per gram. 
T.N.T. (A= 4.3) 
Gun cotton 
Amato) 40/60 (A = 1.3) 
Proc. Roy Soc. A. 
See Journal Chem. Soc. Vol. 119 p.1. Sir R. Robertson. Part t,, £921. 
