1886.] The Flood Rock Explosion. 139 
The atmospheric wave.—The vibrations of the air were exceed- 
ingly slight, owing to the heavy tamp of water. The greatest 
fall of the barometer was .02 of an inch. The wind being in the 
west and blowing eight miles per hour, the slight atmospheric 
wave was naturally carried out to sea, so that its duration and ex- 
tent are lost. 
The earth wave.—The velocity of the earth vibrations was one 
mile in seven-tenths seconds at the outset, decreasing to one mile 
434ths seconds, as far as measured. The notated diameter of the 
shock was 394 miles long. Itis safe to approximate the diame- 
ters (supposing that observers had been on the watch at sufficient 
distances) at 800 miles. For if-the shock was sufficient to reach 
the Cambridge observatory, 197 miles distant, in 194 seconds, and 
shake that eternal structure as it had never been shaken before, it 
ought to have doubled the distance with some perceptible effect, 
giving a radius instead of a diameter of 394 miles. 
Scientific value of the observations —The Flood rock explosion 
cannot be called a surface disturbance because it occurred at the 
sea level. Volcanic and geyser eruptions vary in altitude and 
have a vibratory power downward. All of the vibratory power. 
at Flood rock was upward, which makes its effect all the more 
wonderful, since the farther the shock traveled the more of the 
earth surface it had to lift on account of the constant rise above 
sea level. Enough explosives were used to have obliterated 
Manhattan island if placed on the surface, or to have leveled 
Mt. Washington. The fact that 300,000 pounds of explosives 
will affect a surface of 300,000 square miles does not necessarily 
settle the question as to the cause of earthquakes. It does not 
verify the belief that explosions of some kind cause earthquakes, 
but leaves us in the dark as to the composition of such explo- 
Sives. What mighty ingredients combined to lift the bowels of 
Krakatoa five and ten miles in the air, and so envelope the whole 
globe in a nebula of dust that the sun turned green and the sun- 
Sets were framed in gorgeous hues, lighting up the night long 
after the orb had disappeared? What mighty ingredients com- 
bined to explode Java and overwhelm 100,000 people? What 
Chemicals combine beneath the Yellowstone park and hurl the 
boiling waters from Old Faithful geyser every hour, from the 
Minute Man once per minute, from clusters of geysers all at 
once every day at 4 P. M., from Hell’s Half-Acre once per year 
