r. Continued movement will give the brecciated fragments
of sandstone a rounded form by rubbing them against one another, and, in
this way, a crush-conglomerate is produced. Great masses of limestone in
the Alps, Scottish Highlands, and all regions of intense folding are
thus converted into breccias. Cherts frequently also show this
structure; igneous rocks less commonly do so; but it is perhaps most
common where there have been thin bedded alternations of rocks of
different character, such as limestone and dolerite, limestone and
quartzite, shale or phyllite and sandstone. Fault-breccias closely
resemble vein-breccias, except that usually their fragments consist
principally of the rocks which adjoin the fault and not of mineral
deposits introduced in solution; but many veins occupy faults, and hence
no hard and fast line can be drawn between these types of breccia.

A third group of breccias is due to movement in a partly consolidated
igneous rock, and may be called "fluxion-breccias." Lava streams,
especially when they consist of rhyolite, dacite and some kinds of
andesite, may rapidly solidify, and then become exceedingly brittle. If
any part of the mass is still liquid, it may break up the solid crust by
pressure from within and the angular fragments are enveloped by the
fluid lava. When the whole comes to rest and cools, it forms a typical
"volcanic-fluxion-breccia." The same phenomena are sometimes exemplified
in intrusive sills and sheets. The fissures which are occupied by
igneous dikes may be the seat of repeated injections following one
another at longer or shorter intervals; and the latter may shatter the
earlier dike rocks, catching up the fragments. Among the older
formations, especially when decomposition has gone on extensively, these
fluxion and injection-breccias are often very hard to distinguish from
the commoner volcanic-breccias and ash-beds, which have been produced by
weathering, or by the explosive power of superheated steam.
(J. S. F.)

BRECHIN, a royal, municipal and police burgh of Forfarshire, Scotland.
Pop. (1901) 8941. It lies on the left bank of the South Esk, 7-3/4 m.
west of Montrose, and has a station on the loop line of the Caledonian
railway from Forfar to Bridge of Dun. Brechin is a prosperous town, of
great antiquity, having been the site of a Culdee abbey. The Danes are
said to have burned the town in 1012. David I. erected it into a
bishopric in 1150, and it is still a