452 H. S. JEVONS, H. I. JENSEN, T G. TAYLOR AND C. A. SUSSMILCH. 



The foregoing are the exposures which have provided 

 most of the material, but there are a few other shallow 

 workings, and numerous natural crags and outcrops of 

 weathered rock, especially on the eastern ridge or "shank" 

 of the hill. Our work has been hampered for want of 

 exposures only in connection with determining the outer 

 boundary of the mass, and in trying definitely to decide 

 whether the inner area of shale is connected with the shale 

 outside along the creek or not. 



4. Shape and Thickness of the Mass. 



The shape of the Prospect intrusion can be inferred from 

 inspection of the map in conjunction with the cross section 

 which accompanies it, and it is found to be peculiar and 

 difficult to explain. The line of section shown upon the 

 map (Plate XXXIV) passes nearly east and west through 

 the centre of the mass, and was chosen as being that along 

 which the exposures gave the most precise information. 



In the middle of the intrusion is seen a thin layer of 

 Wianamatta shale resting upon the outer layer of compact 

 igneous rock, which we propose to call pallio-essexite, 1 which 

 in turn rests upon the main mass of essexite. (Figs. 1-3). 

 Both to east and west the junction of the intrusive rock 

 with the shale rises, until first the pallio-essexite is un. 

 covered, and then the essexite. Unfortunately no section 



1 The prefix pallio- has been adopted by Mr. Jevons as part of his 

 systematic nomenclature of igneous rocks, to denote the compact envelope 

 of rapidly cooled rock which encloses every intrusion, from pallium, a 

 mantle or cloak. We see no reason why the use of this term should be 

 confined to a particular system of nomenclature, and believe that it could 

 be compounded with names at present in use with much advantage in 

 clearness and brevity of expression. Thus pallio-granite would signify 

 the rock, usually a quartz-porphyry, which occurs on the border of a 

 granite mass a little way within the contact. Further from the junction 

 the rock assumes the character of a granite-porphyry, and it might be 

 denoted sub-pallio-granite. It is also convenient to use the word pallium 

 to denote the compact outer envelope of a mass without special reference 

 to the kind of rock which composes it. 



