Preliminary Note. 89 



views arrived at are simply the result of an extended and 

 detailed study of the phenomena observable in the field. 



Apart from the chief object of the investigation — i.e. the 

 mode of the occurrence of the phsophate deposits — it was 

 intended to show the distribution of the rocks over a 

 typical area which should include the chief mines of the 

 district, and in this way it became necessary to attempt a 

 delimitation of certain limestone areas, in doing which the 

 following features were brought forcibly to light. 



Their mode of occurrence was extremely indefinite and 

 irregular. Although great pains were taken it wa» found 

 impossible in most places to draw any very sharp line be- 

 tween the limestones and the surrounding rocks. 



They contained inclusions of gneissic and other associated 

 rocks in the form of bands, nodules, etc. 



The proportion of this included rock in relation to the 

 limestone proper was extremely variable so that whilst at 

 some places limestone with inclusions might be a fitting 

 designation, at others one would rather describe as gneiss 

 with intercalated ribbons or bands of calcite. Thus, in 

 passing from a limestone area on to another rock, it became 

 a question of percentage as to where one would draw a line 

 between the two and in the area of gneiss, etc., proper, one 

 would often find little scattering patches of limestone. 



These limestone areas show a very constant and more or 

 less definite striping or parallel structure which always 

 maintained a marked parallelism with that of the surround- 

 ing gneiss in all its variations of direction. 



On close observation, the inclusions in these limestone 

 areas, show some very interesting features. In shape they 

 are varied. One exposure might show a number of con- 

 torted bands of gneissic material running parallel to each 

 other, separated by limestone, and much thickened at the 

 sharp bends by doubling. At other places these inclusions 

 form a comparatively small proportion of the rock mass 

 showing as detached nodules, of irregular shape. These 

 nodules are very commonly roughly lenticular, showing a 

 tendency to taper off at either end along the striping of the 



