EXPLANATION OF PLATES 383 



Plate 57. — Tangents to Curves of Grain — Narroiu Contact Zone 



This plate is based on plate 55, and is for similar conditions. The full lines 

 show tangents to the curve of grain of an injected igneous sheet (supposing the 

 same to be proportional to the square root of the slowness of cooling) as derived 

 from the approximate equations referred to in the text. The position of the point 

 relative to the margin is represented by horizontal coordinates, the average linear 

 dimensions of grain corresponding by vertical coordinates, while the decimals 

 attached to each curve show the ratio corresponding to it of the consolidation — 

 to the initial temperature. The lines in dashes are the actual curves sketched in, 

 where they diverge markedly from the tangents. 



