288 Professor Sedgwick and Mr, Murchison on the 



Age of the Sedimentary Deposits of the Hartz. 



Having thus considered the general structure of the Hartz, we next come to 

 consider the age of its sedimentary deposits. That in their structure, their strike, 

 their accidents of position, and their fossils, they present the closest analogies to 

 the rocks of the Rhenish provinces, is easily shown ; but in explaining the relations 

 of the subordinate formations to one another, we are, for reasons already stated, 

 involved in the greatest difficulties. There are, however, among the fragmentary 

 masses of the Hartz a few sections which give a pretty clear indication of natural 

 groups, especially when put in comparison with the still clearer sections of West- 

 phalia. We will first shortly notice one or two sections on the north-western side 

 of the Brocken. 



Section from Osterode to Clausthal. 



In ascending from Osterode to Clausthal we crossed one of the great spurs of the Hartz, composed of 

 alternating beds of griti psanimite and shale, striiiing about N.E. and S.W., and dipping at a great 

 angle, sometimes N.W. and sometimes S.E., the latter dip being most prevalent. The sandstones were 

 generally in thin hard irregular beds, from one to four inches in thickness ; more rarely in well-defined 

 beds from six inches to two feet in thickness ; their colours were grey, greenish-grey, mottled, purple 

 and reddish ; and sometimes almost black, from the carbonaceous stains diffused through them. The 

 alternating shales were generally thin-bedded, of bluish grey and purple colours, and had, here and there, 

 much carbonaceous matter between their laminae. During the traverse we hardly saw a rock we might 

 not match among the culm-measures of Devon ; and here also, as in Devon, we found an indefinite 

 number of impressions of small reeds and grass-like plants. The rocks above described are broken 

 through and interfered with by masses of greenstone, amygdaloid, &c., ranging nearly parallel to the 

 prevailing strike ; and the whole system is continued till it is lost under the alluvial covering near 

 Clausthal. 



Section from Clausthal to Griind. — (PI. XXHI. fig. 18.) 



In making this traverse by the mine-works, we first crossed a series of beds dipping S.E. at a consider- 

 able angle, but not without the interruption of many great irregular flexures. They contained a few 

 impressions of plants, and could not be mineralogically distinguished from many parts of the culm-mea- 



England there is no analogy whatsoever ; though such was formerly supposed, and might seem indeed to 

 be implied in some of the sections of Hoffmann. Though the carboniferous beds on the southern flanks 

 of the Hartz may seem to confirm the opinion, that the coal formation is but an accidental deposit sub- 

 ordinate to the red sandstone (mw accident dans Ic gres rouge), they do not represent the great carboni- 

 ferous systems of Westphalia and Belgium ; and still less the carboniferous system of Great Britain. In 

 further confirmation of this opinion, we may state, that true coal plants and thin carbonaceous laminae 

 occur in great abundance in the lower division of the new red sandstone, between the magnesian lime- 

 stone and the rich coal formation of Whitehaven, and also in the same formation near Birmingham (see 

 Silur. Syst., p. 55, and note, p. 56). We have only to suppose these plants and carbonaceous bands more 

 largely developed, so as to form beds of coal, and we shall then have an upper division of the coal for- 

 mation precisely in the position of that of the Hartz. 



