HYPOTHETICAL STAGES LEADING UP TO THE KNOWN ERAS. 103 



were reached. Local spots of fusion must thus arise. To this fusion, 

 the entrapped and occluded gases may be presumed to have contrib- 

 uted, and to have joined themselves to the fused masses, and to have 

 aided in giving them fluidity. 



The dynamics of ascension. — As the rise of temperature continued, 

 more and more of the mixed material reached the fusing-point, while 

 other material so nearly approached it as to become plastic and per- 

 mit readjustive movements. In this way, fused parts were permitted 

 to join one another and to move in the direction of least resistance. 

 The static pressure from the earth-body itself was always greatest 

 below and least above, but was nearly constant for any given short 

 period. The stresses arising from the differential tide-producing 

 attractions of the sun and moon were also greatest below and least 

 above, but were periodic, stress and relief following one another in 

 semi-daily succession, giving a kind of kneading process (Vol. I, pp. 578, 

 579, and 629-632). These interior stress-differences are thought to have 

 pressed the fused vesicles outward, causing them to unite and form 

 threads or stringlets, which insinuated themselves through the more 

 refractory portions that remained solid, and at length developed into 

 tongues of some volume. As these liquid threads or tongues rose 

 to higher horizons of lower pressures, and hence of lower melting- 

 points, they carried with them a certain surplus of heat above that 

 required to maintain their liquidity in the new horizon, and this sur- 

 plus was available for melting or fluxing their way. They were at 

 the same time, however, subject to loss of heat by contact with sur- 

 rounding rock of lower temperature. They were thus, probably, at 

 the same time taking up fusible material met in their path, and deposit- 

 ing old material as it became less adapted to remain fluid under the 

 new conditions, either because it had reached the point of its satura- 

 tion in the mixed rock-solution that had been developed, or had cooled 

 to its point of congelation. The liquid thread was thus presumably 

 taking on and giving up material continually as it worked its way 

 outward, the process always being selective, and involving the reten- 

 tion of the more soluble or more fusible portions, and the rejection 

 of the less soluble or more refractory portions. Since the included 

 gases may be safely reckoned with the former class, there was a selec- 

 tive accumulation of these, and the ascending liquid became densely 

 charged with them. To this ascensive process, those substances whose 



