1865.] MATTHEW SOUTHERN NEAV BETJXSWICK. 433 



Middle Devonian „ Southern New Brunswick (Dawson). 



„ „ ? Northern Maine (Hitchcock). 



Upper Devonian „ Southern New Brunswick (Dawson). 



„ „ South-easternMaine (Jackson and Bogers). 



„ „ Northern Maine (Hitchcock). 



Lower Carboniferous widespread in Nova Scotia and New Bruns- 

 wick (Lyell, Dawson, &c.). 



Carboniferous „ with the last (Lyell, Dawson, &c.). 



Thus the only important hiatus now remaining is that wherein 

 the Trenton limestones and Hudson-river shales should appear. As 

 great physical changes occurred along the line of the Appalachian 

 chain at the close of the latter period, these formations, if they exist 

 in Acadia, will probably be found to form a part of the Lower Silu- 

 rian already known, possibly the upper beds of the St. John shales 

 or of their equivalent. 



It is now a well-established fact that throughout Palaeozoic time 

 the centre of the North American continent was comparatively stable, 

 the whole series of formations being found in continuous and con- 

 formable succession from the base of the Silurian to the summit of 

 the Permian. To the northward the Huronian series had been 

 uptilted before the Potsdam period. In Acadia, however, the Pri- 

 mordial shales appear to overlie the Huronian without any appreciable 

 discordance between the two. 



Throughout New England and on the borders of Canada East, 

 disturbances occurred at the close of the Lower Silurian age : they 

 appear to have affected all Acadia as well. Dr. Dawson suspects the 

 existence of a break at this point in the continuity of the Silurian 

 sediment of Nova Scotia, and the same also seems to be indicated in 

 the rocks of southern New Brunswick. 



At the junction of the Upper Silurian and Lower Devonian with 

 the higher portion of the latter system, another discordance appears 

 in northern and south-eastern Maine (Hitchcock) and southern New 

 Brunswick. 



But the broadest and most strongly marked line of division in this 

 region, as already stated, is that which separates the Lower Carbo- 

 niferous from the underlying formation. 



There are thus three breaks and possibly a fourth (between the 

 two sections of the Carboniferous system) in the Palaeozoic chain 

 noticeable in Acadia. But while this country has been the theatre 

 of great physical disturbances and heavy accumulations of sediment 

 during those long ages in many parts of it, yet as the strata have 

 to a great extent been exempt from extreme metamorphism, their 

 study will not only add many interesting facts to those already 

 known, but is calculated to throw much light upon the geology of 

 that region. 



Note. — Since writing the above I have seen a collection of fossils 

 lately discovered at a locality within the limits of the district noticed 

 under the head of " Upper Silurian ;" they tend to confirm the views 

 herein expressed regarding the age of the series thus designated. 



