PETROLOGICAL ABSTRACTS AND REVIEWS 477 
hardness were plastic. Fluorite was plastic. Diopside, hardness 5.5, 
developed polysynthetic twins. Apatite showed signs of plasticity. 
Orthoclase ruptured, but the particles were optically deformed. Quartz 
lacked plasticity, while marble was perfectly plastic. Granite suffered 
cataclastic deformation but became gneissose. In Kick’s experiments 
the lateral resistance was insufficient and it was impossible to state how 
much pressure acted on the sample, since it was distributed over 
the metal tube, imbedding substance, and the sample itself. In order 
to overcome this trouble, F. D. Adams and C. G. Coker (1910) devised 
a thick tube of nickel steel, made of a steel block. The receiving tube 
was carefully bored out and polished and was slightly less in diameter 
than the cylinder of rock which was to be tested. The rock cylinder was 
inserted when the tube was hot. The compressing rod which fitted into 
the receiving tube was made of hard chrome-tungsten steel. The cart- 
ridge was weaker near the middle so as to prevent the material from 
flowing around the compressing rod. They succeeded in getting per- 
fectly plastic deformation of Carrara marble and the strength tests 
showed an increase in strength with an increase in the deforming stress. 
The pressure exerted was equal to a depth of 41 miles of the earth’s 
crust. 
The following experiments illustrate the relation of temperature and 
pressure to plasticity. G.Tamman showed that for a series of metals 
an increase in temperature of 10 degrees caused a doubling of the rate 
of discharge through an aperture, all other conditions being equal. 
L. Milch showed that halite, melting point above 800°, is plastic at 200°C. 
Doelter observed that silicates pass through a transition stage of 
peculiar viscosity when passing from the crystalline to the molten state. 
Similarly, A. L. Day and E. T. Allen found that albite could be readily 
bent when in this state. ‘‘Protoklase’”’ (see Rosenbusch, Elemente der 
Gesteinslehre, 65, 3d ed.) is explained by W. Salomon (1910) as the effect 
of the pressure of intrusion on magmas in this state. In rgo01 Nicholson 
and Adams did not succeed in getting perfect plastic deformation of 
marble except at temperatures of 300°-400° C. In 1910, Adams and 
Coker succeeded in getting plastic deformation of marble at a lower 
pressure when it was heated than at ordinary temperatures. 
The value of the time factor in plastic deformation is shown in the 
following experiments, which prove that extended plastication favors 
deformation. In ro1o, F. D. Adams investigated the time factor by 
deforming a marble column one minute and finding on immediate testing 
that it retained 60 per cent of its crushing strength. It retained 65.7 
per cent of its crushing strength when tested 100 days later and retained 
