1822.] Geological Society. 233 



«outh-east of Carenton. At St. Jean, it rests upon argillaceous 

 elate, and to the westward in the neighbourhood of St. Vaast, it 

 is found in a similar position. At Litry, in the department of 

 Calvados, it is supported by the coal measures. 



The top of the Brugcre de Crecy, on the road from Conde 

 sur Noireau to Caen, is formed of a conglomerate consisting of 

 xounded quartz nodules, from the size of a pea to three or four 

 inches in diameter, agglutinated by a hard red argillo-silicious 

 cement, and resting upon nearly vertical strata of argillaceous 

 slate and greywacke, of which, part of the mountain is composed* 

 Near St. Laurent de Condel the same porphyritic conglomerate 

 rises through the oolite formation ; and it is visible between 

 Valagues and St. Vaast. It bears a striking resemblance to that 

 associated with the new red sandstone formation in the neigh» 

 bourhood of Exeter. 



At Litry, ESE. from Bayeux, coal measures occur, resting^ 

 upon argillaceous slate, and occupying an oval space about 1700 

 yards from E. to W. and 850 yards from N. to S. The direc- 

 tion is E. and W. and the dip 22° to N. In general, the quality 

 of the beds is indifferent. 



At May, between St. Laurent de Condel and Caen, the com- 

 pact sandstone that is found overlying the transition limestone^ 

 and forming part of a large denudation in the oolite formation^ 

 has the appearance of old red sandstone. The beds vary much 

 in thickness, are sometimes micaceous, and dip 45° to the N. 

 between Centaux and Langannerie a similar stratum appears 

 ■Tiesting upon quartz rock near the last mentioned spot. 



The general character of the quartz rock that occurs in the 

 departments of Calvados and La Manche is that of indurated 

 sandstone passing in some instances into common quartz. It 

 is found in beds varying from two to eight feet in thickness, and 

 resting on each other ; the colour passing from white or whitish 

 grey to a red tint. The denudations in the oolite formation in 

 this district are formed wholly or in part by quartz rock. Be- 

 iween Tourville and Mondrainville in the road from Villers to 

 Caen, argillaceous slate and greywacke are observed resting on 

 this rock, and dipping with it at about an angle of 45° or 50° to 

 the north. At Falaise, the quartz rock is intersected by similar 

 strata, and in the country between Valogues and Cherbourg^ 

 particularly in the mountain of Le Roule, which rises behind the 

 latter town, the same appearances are observed. In the quartz, 

 rock of Le Roule, cylindrical bodies, like those mentioned by Dr. 

 M'CuUoch, as arising in the quartz rock of Glen Tilt, are occa- 

 sionally found. 



Of the south-western part of the department of Calvados, a 

 considerable part is formed of argillaceous slate and greywacke, 

 extending in a line which passes nearly W. from the neighbour- 

 hood of Perrien to Litry, in a south-eastern direction to Villers, 

 and ESE. to Croix, whence it runs to the SE. and crosses the 



