232 M. DE BONNARD OH the 



tous and grey copper, which has been remarked to me as a 

 circumstance occurring solely in the copper of the Palatinate 

 situated in the porphyry, (Dippenweiler and Creutznach), 

 ■whilst it is stated that the copper veins worked in the trap 

 principally produce carbonate of copper. 



Lastly, it is from the porphyritic rocks, on the banks and 

 even the bed of the Nahe, that the numerous salt springs of 

 the Creutznach rise, and borings through the bottom of the 

 pits in which these springs are collected, have been driven 

 more than fiO metres [about 1 97 feet]) from the surface with- 

 out meeting with any other rock than porphyry. This ap- 

 pears to me a very remarkable fact, and I consider it unique 

 in the history of salt springs, wiiich every where else rise 

 from rocks of sediment. The springs of Creutznach are of 

 a temperature a little above that of the mean temperature of 

 the atmosphere ; they contain only about a hundreth part of 

 marine salt, and with this salt muriates of lime and magnesia 

 and a little bitumen, but not an atom of the earthy and air 

 kaline sulphates, which occur in all the saline springs of the 

 E. of France and the N. of Germany. 



To complete the notice of all the localities in which I have 

 observed porphyry, I should add that the summit of the 

 Landsberg, near Obermoschel, presents steep rocks appa- 

 rently of the same nature, and which have also been thought 

 to have been met with in the mines of that mountain, and 

 in those of Stahlberg ; but, as I have already had occasion 

 to state, these two mountains are so much disturbed, and 

 they contain, especially the former, so many different rocks, 

 with so much disorder manifested in their union, that it ap- 

 pears to me no conclusion can be deduced from the obser- 

 vations to which they give rise, for determining the relative 

 age of the different rocks of which they are formed. Ab- 

 stracting therefore these two last positions, I shall cast a 

 coup d'oeil over the porphyritic rocks I have just menr 

 tioned. 



Many geologists have apparently regarded them as con- 

 stituting part of the trappean formation of the Nahe,* and 



*M. Omalius d'Halloy, Journal des Mines, No. 144; M. Calmelet, 

 Journal des Mines, No. 146, p. 142. 



