ROCKS OE BOHEMIA. 599 



the Lake district in rocks af about this age. Other localities for 

 mica-traps are recorded by Professor Bonney (Q,. J. G. S. vol. xxxv. 

 p. 165) . In a paper by Messrs. Gunn and Clough on the Silurian 

 beds of Teesdale (Q. J. G. S. vol. xxxiv. p. 30) it is stated that "no 

 mica-trap dykes are know^n in the Carboniferous beds of this district, 

 or of any other part of the north of England, while such dykes are 

 common in the Silurian districts of the Lake-country." The 

 Bohemian mica-traps afford a remarkable additional case, which 

 can hardly be a mere coincidence. 



Porphyrite. There appears to have been an overflow of porphyrite 

 lavas during the deposition of d 1 a & /3. Above the conglomerate 

 of d 1 a near Skrey occurs a great series of porphyrites and asso- 

 ciated ashes and breccias, and a similar series is seen above the beds 

 of d 1 /3 near HudUce (fig. 2), also with ashes, breccias, and aggio- 

 meratic beds. These porphyrites are usually of a dull claret-red, 

 with small plagioclase crystals, visible to the naked eye, and are 

 very frequently amygdaloidal. 



Diabase occurs intrusive in soft shales of Precambrian, Cambrian, 

 and Silurian age, often running parallel to the bedding for some 

 distance. It is excellently exhibited in the neighbourhood of 

 Kuchelbad, especially opposite the inn of Vyskocilka, where it is 

 intrusive in the shales of E e 1, which it frequently alters, both above 

 and below. The diabase here exhibits beautiful spheroidal weather- 

 ing ; and similar weathering is seen in a mass of diabase intrusive in 

 the shales o f the colony at Hodkovicek. It often contains fragments 

 of the rocks into which it intrudes : at Butovice, where it is intrusive 

 in limestone bands near the summit of e 1, which are composed 

 largely ot OtrJiocerata, the diabase itself contains many fragments 

 of these Cephalopods, free from matrix, as discovered by M. 

 Barrande. 



Diorite occurs as dykes intruded usually into the older rocks of 

 the basin. The dykes are generally fine-grained, have undergone 

 considerable alteration, and are of little interest. 



Eclogite (serpentine of Hauer's map). In describing the Pre- 

 cambrian rocks of the neighbourhood of Budweis, it was stated that 

 there was a mass of eruptive eclogite in the neighbourhood of 

 Chlumi^'ek, which seemed to have converted the gneiss of the Pre- 

 cambrian series into a garnet rock. The gneiss seemed to me to 

 become more granatiferous as it approached the eclogite, until at last 

 all the black mineral (hornblende ?) disappeared, and a white matrix 

 containing amber-coloured garnets remained. On examining Hauer's 

 map of Bohemia, it will be seen that the garnet rock which occurs 

 to the west of Budweis does not run in the direction of strike of the 

 Precambrian rocks, which is nearly E. and W., but surrounds 

 masses of intrusive eclogite (serpentine of map). On the same map, 

 also, it will be seen that other masses of garnet rock (as south of 

 the Danube, near Krems, and some miles to the west of Gmiind, &c.) 

 are invariably accompanied by masses of rocks mapped as ser- 

 pentine. Hence the connexion does not seem to be accidental, and 

 it appears probable that the metamorphic garnet rock is due to the 



