SCAGLIA OF THE ALPSa 



205 



chalk, and present no indications of any interruption in the regular 

 series of successive deposits. In an interesting paper, by Professor 

 Sedgwick and R. J. Murchison, Esq. on the relations of the secon- 

 dary and tertiary strata on the southern flanks of the Tyrolese Alps, 

 published in the Phil. Mag. for June, 1829, the tertiary strata are 

 described as forming a vast series of beds resting on scaglia or chalk : 

 the lowest of these beds contain, exclusively, the remains of marine 

 animals, and no interval of repose can be traced between the epochs 

 of the formation of the secondary and tertiary strata. The scaglia 

 occurs in beds nearly vertical ; the upper ones contain nodules and 

 layers of flints : their colour is red, and their structure fissile. The 

 lower beds are thicker, and more compact, and pass into a beautiful 

 white saccharoid marble. The scaglia contains in some parts ammo- 

 nites and belemnites. It cannot, however, be denied, that where the 

 beds are so much broken and contorted as they are on the Tyrolese 

 Alps, and where their mineral characters differ so much from the 

 beds of the chalk formation in England and France, it becomes ex- 

 tremely difiicult to ascertain the identity of these secondary depo- 

 sitions in distant countries. In the calcareous formations of the Savoy 

 Alps, 1 not only discovered the characteristic fossils of the English 

 strata, but observed some of the beds possessing the true mineral 

 characters of the English oolites, and lias ; but where these charac- 

 ters are entirely wanting, and where, from the overturning and con- 

 tortion of the strata, the aid of relative geological position cannot 

 • be obtained, the inferences from a few fossil organic remains must 

 be received, with a certain degree of caution. 



