Jean-François Berger

Name: On the Dykes of the North of Ireland
Author: Jean-François Berger

On the Dykes of the North of Ireland (1816)

Summary

“On the Dykes of the North of Ireland”, published in 1816, is a work by Jean-François Berger. It explores elements such as dykes, strata and Somma.

Quotes from On the Dykes of the North of Ireland (Jean-François Berger)

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ The induration which the secondary rocks undergo when traversed by dykes has often been noticed; it is not my intention now to discuss this subject; I shall only mention that the induration does not extend far from the dyke, and that the phenomena though very frequent are not universal. [4] I have only noticed one instance of remarkable change in a primitive rock contiguous to a dyke. In the case I allude to, viz. in the lead mine of Kildrim in the county of Donegal, mica slate adjacent to the dyke had its texture quite loosened, and was in a dusty state. ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ It is very evident from these observations that some of the dykes at least were formed at a later period than the metallic veins; an inference that might be extended to all, could we show them to be all contemporaneous. That they are so is rendered probable by their parallelism, and by the nearly uniform texture of the trap, in whatever rock the dyke is found. The simple minerals too contained in the trap favour this opinion. Calcareous and heavy spar, and lime intimately mixed with the trap abound most in the dykes of secondary rocks ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ In general there is no foreign matter between the substance of the dyke and the rock it divides, excepting a slight rusty appearance on the surface of the latter. The contact between the two is pretty close, but they may always be disjoined by the blow of a hammer. ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ The depth to which the dykes descend is unknown; and after having observed the sections of a great many along the coast in cliffs from 50 to 400 feet in height, I have not been able to ascertain (except in one or two cases) that their sides converge or have a wedgeform tendency; so that no estimate can be formed of the depth at which they terminate. ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ The principal differences between the two are, the constant uniformity of the Antrim strata, the homogeneity of their matter, their basaltic form, and the much greater depth of the strata, which are seldom less than twenty-five or thirty feet, and the less rapid inclination inwards of the strata, which there seems not to exceed an angle of fifteen or twenty degrees, whereas here in Somma the angle is not less than from forty to forty-five degrees, which in both amounts nearly to the angle of the dip of the outward surface of the hill which they compose. ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ There is not that variety in the substance of the dykes, that their numbers, their distance from one another, and the varied nature of the rocks which they intersect would lead one to expect. I have found them composed of the following rocks, which are introduced in the order of their most frequent occurrence. Trap and greenstone, with their associates Lydian stone, flinty slate, greystone and wacke. ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ The conclusion to be drawn from this table is that the bearing of the dykes is from S.E. to N.W., and that the dykes all cut the planes of the strata through which they pass, at very considerable angles.
A shift in the direction of a dyke is an accident of rare occurrence ”

[↩︎]

Source: Wikisource

Jean-François Berger, On the Dykes of the North of Ireland (1816)

“ In this respect therefore they do not seem to agree with the metallic veins.
Moreover, I have not observed that they branch off into slender strings, or (except in some very rare instances) that they swell into (what the miners term) bellies, after the manner of the metallic veins.
The dykes, whether they occur in primitive or secondary countries are nearly vertical. The mean angle of deviation from the perpendicular deduced from nine cases occurring in primitive rocks was 13°, the extremes being 9° and 20°. ”

Jean-François Berger

Summary

Quotes from On the Dykes of the North of Ireland (Jean-François Berger)

Common terms

Similar works

Get perspective with Kwize: daily news enlightened by great literature