687 
From what has already been sa,id regarding the age of the upheaval of the coral reefs, 
it will be seen that there is not necessarily anything in Mr. Maitland’s suggestion 
inconsistent with the assignment of an early Tertiary, or Pre-Tertiary, date to the 
Boioro Limestones. 
From observations made by Mr. Maitland at Millport Harbour, it is evident tnat 
the Boioro Limestones have a thickness of at least 800 feet. 
METAMORPHIO ROCKS. 
The approximate definition of the area occupied by these rocks, in which, and the 
granitic and other plutonic rocks, deposits of the “ precious ” and less precious metals 
may be looked for, is, from an economic point of view, one of the most important 
results of Mr. Maitland’s observations. 
The Metamorphic Eocks are separable, according to Mr. Maitland, into two broad 
subdivisions. “ The first includes what may be called the crystalline schists, and the 
second comprises all those other rocks in which the alteration has not gone sufficiently 
far to conceal their clastic or derivative nature. To draw a line separating the two 
divisions is quite impossible at present.” 
An immense area, extending for a few miles back from Port Moresby, nearly to 
the 8th parallel of South Latitude (the German Boundary) is occupied by Metamorphic 
rocks. Another large area occurs on the Mainland to the east, at Mount Suckling. 
Although unexplored, the greater part of the intervening district, and indeed probably 
the greater part of the highland interior of Hew Guinea, may be conjectured to be of 
similar constitution. The islands of the D’Entrecasteaux and Louisiade Groups, 
several of which are known to be auriferous, are also mainly composed of metamorphic 
rocks. It will remain for future geologists to determine whether, among these rocks, 
the representatives of our “Gympie” and “ Burdekin ” Formations, and of the still 
older formations not yet recognised in Queensland, are to be distinguished. 
IGNEOUS EOCKS. 
From Mr. Maitland’s Maps it appears that volcanic rocks are met with at intervals 
from the Douglas Eiver (Long. 141° 15' E.) to the Eastern end of New Guinea and 
throughout the D’Entrecasteaux Islands, where they occupy considerable areas. In the 
Louisiade Archipelago they seem to occur more sparingly, or, at least, they have not 
been noted east of Long. 162° 40', where they form some of the smaller islands of the 
group. Mr. Maitland says that “ the Volcanic rocks fall into two primary divisions, 
the Acidic Series and the Basic Series, the former of which appears to predominate. 
Eepresentatives of the Trachytic, Andesitic, and Basaltic lavas, with their associated 
fragmental beds, were met with throughout the Possession. From the fact that these 
rocks rest, with a violent uneonformability, on the most recent strata, they cannot be of 
any very great age.” „ . 
Interesting particulars are recorded of some forms of modified volcanic activity 
in the D’Entrecasteaux Islands and the Mainland of New Guinea. 
In Fergusson Island, the largest of the D’Entrecasteaux Group, Captain 
Moresby, Mr. Andrew Goldie, Mr. Basil H. Thompson, and Sir William Maegregor 
have noted the occurrence of thermal springs. Sir William records that “ the whole of 
the low country near Seymour Bay contains, here and there, over an area ot, perhaps, 
eight or ten square miles, boiling springs, saline lakes, and thousands of fumaroles, 
giving out sulphur fumes.” Mr. Thompson describes “ springs of boilmg water and 
boiling mud,” and adds that “in one instance boiling mud was spouted up trom a 
chimney-like cavity in the hillside,” 
