166 The N.Z. Journal oe Science and Technology. [Sept. 
of the globe. Slight stress-changes affecting extensive perilithic belts may 
induce intense tumefying action which strains the volcanic edifice to the 
breaking-point. Tilts, tremors, volcanic eruptions, and earthquake swarms 
result. 
11. Deep tumescence occasions simultaneous tilt and tremor, which act 
slowly through weeks preceding eruption. 
12. At the Hawaiian Observatory east tilt precedes visible rising of lava 
by eighteen days, and west tilt precedes sinking of lava by a like interval. 
The beginnings of rapid forced movements away from the volcanic centrum 
exhibit the most perfect accordances with the subsequent lava-risings. 
13. Allowing for diurnal temperature effects, which are measured and 
definite, the longer-term tiltings resolve themselves into quasi-rhythmic 
decaying series of tilt waves, the series of quarterly, and the waves of 
monthly, period. These groupings suggest a solar and a lunar causation. 
The angular amount of the tiltings is excessive. The mean directions are 
away from and towards the volcanic centrum. The subsequent lava- 
movements show similar rhythms. 
14. Quick microtremor of one-fifth-second period occurs in spasms which 
in frequency and amplitude vary directly with angular amounts of tilting. 
Harmonic micro tremor of slower period also occurs, and tends also to vary 
in amplitude with the tilting. The harmonic tremor has definite N.E.-S.W. 
direction of propagation. 
15. Local earthquakes have maximum intensity and minimum frequency 
when the lava is lowest and the crater-orifices are clogged. Maximum 
frequency and moderate intensity occur when the lava is flowing freely and 
effervescence in the crater-pits is abundant. 
16. In contrast to tilt and tremor, increased frequency of local earth¬ 
quakes shows instantaneous agreement with times of rising lava and high 
lava culminations. 
17. The distances of local earthquake origins, judged by measurement 
of preliminary tremors, accord with Mauna Loa distance from station for 
Mauna Loa eruptions, and for Kilauea activities a much shorter distance is 
indicated. Slow subsidences of Kilauea lava culminate in earthquakes at 
Mauna Loa distances. Rapid subsidences of Kilauea lava usually follow 
earthquake swarms which began at Mauna Loa distances. 
18. Earthquake frequency and lava culminations of rising both show 
tendency for crests to occur near equinox with some lag after equinox. 
The troughs appear to be reactions following the equinox effect. 
19. In a rough way weekly earthquake frequency expresses the rate of 
movement of the lava-column and the quasi-rhythmic monthly period. 
Instrumental Equipment. 
For measuring tilt, tremor, local earthquakes, and distant earthquakes 
at least two pairs of horizontal pendulums are necessary. For practical 
purposes optical registration is not necessary, though it may be desirable 
if vertical component registration and tilt-free records of teleseismic 
disturbances are sought. A series of seismometric experiments at the 
Hawaiian Observatory, by Dr. Arnold Romberg and the writer, demon¬ 
strated that for quick local movements smoked paper is better than bromide 
paper, as a very quick vibration may fail to register photographically. 
Horizontal pendulums are simple to construct, but the chronograph-drum 
must have an equable rate, and the transmission-levers require some 
delicacy of adjustment. 
The clinograph, or tilt instrument, consists of a light boom 10 ft. long 
suspended from a 4-foot pier with a 10 lb. weight near the end hanging in 
