What made the favoring conditions which have helped on the influence of its metamorphic tendencies, so as to produce still more sensitive and variously-changeable portions of organic matter?
Besides the stratified and massive rocks, there is still a third set, produced by the contact of these two, and called, in consequence of the changes thus brought about, the Metamorphic rocks.
The Metamorphic Rocks are sometimes described as "Aqueo-igneous," since both water and fire helped in the forming of them.
Mona marble is an ophicalcite from the metamorphic series of the Isle of Anglesey, while the "Irish green" of architects is a similar rock from Connemara in western Galway.
Certain calcareous metamorphic rocks frequently form stones which are sufficiently beautiful to be used for ornamental purposes, and are generally classed as marbles.
In this second study I have attempted to solve the problem as to whether such an innate inciting power can be shown to exist by comparing the forms of the two chief stages of metamorphic species, or whether such a force can be dispensed with.
We therefore see, in this case, the combination of a metamorphicand a direct development taking place to a certain extent under our eyes.
In the second essay the attempt was next made with reference to double form-relationship, as presented for observation in metamorphic insects, to draw conclusions as to the causes of the transformations.
Syenite, like granite, is recognised as an igneous as well as a metamorphic rock.
What are some of the appearances relied upon for distinguishing metamorphic from igneous granite?
Some geologists consider it to be invariably an igneous rock; but, as just stated, it sometimes passes into gneiss in such a way as to lead us to infer its metamorphic origin.
Granite is recognised as an igneous as well as a metamorphic rock.
But, for sake of clearness, we have reserved special account of the structure and mode of occurrence of metamorphic and igneous rocks to this place.
What kinds of rocks are embraced by the Metamorphic class?
Metamorphic and Igneous Rocks--mode of their occurrence.
There has been much difference of opinion as to the origin of granite--some holding it to be an igneous rock, others maintaining its metamorphic origin.
Frequently, it is quite impossible to say what was the original condition of some metamorphic rocks; often, however, this is sufficiently obvious.
It occurs in beds (talc-slate), and is often met with in districts occupied by metamorphic crystalline rocks.
His observations on the geology of South America were given in a masterly essay, and these and subsequent researches threw much light on igneous and metamorphic phenomena and on the resulting changes in rock-formations.
The Relations of the Silurian and Metamorphic Rocks of the south of Norway," ib.
There is no igneous, no metamorphic rock here; nothing but limestone of the Jurassic formation.
Beyond, the metamorphicrock gave place to red sandstone, and the ground sloped down into the little coal basin of Firmi.
In many other cases the metamorphic process itself remains a mystery, and from the nature of the products alone do we conclude that such a metamorphic action has taken place.
The same materials yield the most dissimilar products, a fact that is of the greatest importance in reference to the study of the nature of erupted rocks, and of the metamorphic action which they occasion.
There are several small hills of igneous rocks to be met with, also metamorphicschists and other deposits that have no uniformity in their distribution over the country, which gives better hopes of rich gold deposits being discovered.
It is pleasantly situated between low ranges of metamorphic hills that run east and west, and is south of the Magalisberg mountains seven miles.
Ironstone and iron-conglomerate are plentiful over this part of the country; blue metamorphic rocks crop up between slate shale and quartz, similar to that of the Tati gold-fields, in all directions.
But not a few controversial questions were dealt with, and the famous 'metamorphic theory' was advanced in opposition to the Wernerian hypothesis of 'primitive formations.
We feel no hesitation in deciding it to have been a silico-argillaceous white sandstone, now almost granitized by extensive metamorphic action.
The fossils are few, obscure, and seldom met with in the lowest fossiliferous series; and the transition is very gradual from the distinctly metamorphic to the fossiliferous rocks.
The changes have at least been sufficient to justify their being characterized as metamorphic rocks.
And such is the condition in which the metamorphic strata are actually found.
It is the opinion of some geologists that there is another system situated between the metamorphic rocks and the silurian system.
On this account Mr. Lyell proposes to call them metamorphic rocks.
By what agency have the changes in the metamorphic rocks been effected?
They have been subjected to a very high degree of metamorphic action, and yet strata intimately associated with them have, in occasional instances, contained fossils.
The conversion of the lower sedimentary strata into metamorphic rocks has been effected by volcanic heat.
Give the instance of metamorphic action from intrusive granite in Norway.
It is doubtful whether the roofing-slates should be considered as belonging to the metamorphic series or not.
Wherever the heated material came into contact with aqueous rocks it transformed them, for a foot or more, into crystalline, metamorphic rocks.
The most enduring of all the rocks are the foundation granite, and the metamorphic rocks that lie next to them.
From aqueous rock materials, fire has produced a metamorphic rock.
As bricks vary in colour and quality according to the materials that compose them, so the metamorphic rocks differ.
If mica is a prominent element, the metamorphic rock is easily parted into overlapping, scaly layers.
A very hard conglomerate, similar in character to that of the upper Indus and of the Giah ravine, was also observed at intervals, alternating with very highly metamorphic slates.
About half-way down, the amygdaloid was replaced by metamorphic slate, and for the remainder of the descent the rocks were alternations of slate, very hard conglomerate, and quartz rock.
On the northern face of this range, between Pata and Dadu, the sandstone, which had continued since I left the valley of the Tawi, was replaced by a succession of metamorphic slates, sometimes very micaceous.
Granite occurs in great abundance, sending immense veins in all directions into the metamorphic rocks, which are seen to be everywhere upheaved and dislocated by the injected mass.
In one place only metamorphic slate was seen below it, dipping at a high angle to the north-east.
We find there a series of narrow arms of the sea, stretching far into the land, and separated by rugged and generally steep ranges of metamorphic or plutonic rocks.
On the right side there were indications of stratification on the steep sides of the mountains, and, from the colour, the rock there appeared to be partly granite and partly metamorphic slate.
The igneous rocks, then, are the lowest of all; then come the metamorphic rocks; and as before stated, on top of metamorphic rock begins the first evidence of life in its lowest form.
To metamorphose is to change; and metamorphic rocks are those which have been changed by heat or pressure from their original formation.
The metamorphic rocks were primarily igneous and are changed somewhat in their structure by the lapse of time.
The first and oldest division is called the "Silurian" age, which is underlaid by the metamorphic rocks and overlaid by the rocks of the Devonian period.
I had an extraordinary experience with it last night.
But I can at least describe the woman to the smallest point.
And yet I find it so interesting, so fascinating, that even now I will keep it in its place.
It is formed of a compact light grey metamorphic rock, and was formerly in the collection of the Rev.
These are usually of clay-slate, or of somemetamorphic rock.
They are for the most part made from metamorphic or volcanic rocks, and occasionally from quartzite, but I have never seen a British perforated axe made from ordinary flint, though hammers of this material are known.
Some Irish celts, formed of different metamorphic rocks, present the same forms as those of Figs.
A remarkably elegant instrument of this kind, formed of a quartzose metamorphic rock, striped green and white, and evidently selected for its beauty, is in the well-known Greenwell Collection.
They are usually formed of some igneous or metamorphic rock, and vary considerably in size, some being as much as 10 or 12 inches in length.
In the same collection is another specimen, found near Fimber, formed of a green metamorphic rock.
The silver-bearing metamorphicrocks of Cartagena, and a portion of the slopes of the Sierra Nevada are classed in the Permian formation.
In the older rocks, basalt has often undergone decomposition into melaphyre; and amongst the metamorphic rocks it has been changed into diorite or hornblende rock; the augite having been converted into hornblende.
There can be little doubt that amongst themetamorphic rocks of Galway, Mayo, and Donegal the great beds of (often columnar) diorite were originally augitic lavas, which have since undergone transformation.
The diorites are abundant as sheets and dykes amongst the older palaeozoic and metamorphic rocks, and are sometimes exceedingly rich in magnetite.
The foundation rock is sometimes metamorphic schist, or gneiss, at other times sandstone referred by Hislop to Jurassic age; and in no single instance has a volcanic crater or focus of eruption been observed.
Sometimes, however, owing to a sudden adventurous spirit appearing in the land, a nation’s Classical tradition is broken by popular ridicule and the reappearance of young Metamorphic Poets.
In Adelie Land the rocky outcrops are metamorphic sediments and gneisses.
The "erratics" comprised a great variety of metamorphic and igneous rocks, and, on a more limited scale, sedimentary types.
