330 Reviews — Dawson's Acadian Geology. 



mined satisfactorily, but estimates of the time required for their 

 occuiTence are of necessity purely hypothetical. Any help to the 

 discovery of a trustworthy time-measurer would be of great service. 

 In the history of the Micmacs and in the succession of forests, in the 

 same localities, resulting from natural causes, and within a known 

 time, Principal Dawson believes that he has data for maintaining 

 that a much shorter period was required for the ethnological and 

 pliytological changes in Denmark and other places than is generally 

 demanded by antiquarians. 



The Glacial phenomena, with the associated drift, are ascribed to 

 the action of the sea and its currents bearing ice at certain seasons 

 of the year, accompanied with a gradual subsidence and re-elevation 

 of the land, while the action of Glaciers was very subsidiary. 

 Considerable confusion has arisen from generalizing on the origin of 

 Boulder-clays from observations made in circumscribed localities. 

 The Boulder-clays of the South of England differ, as is well-known, 

 from those of Scotland. They contain boulders from distant 

 localities, associated with some obtained from neighbouring rocks, 

 while in Scotland the deposits are local, all the boulders being 

 derived from higher portions of the water-system in which they 

 occur, and the clay itself deriving its colour from the predominant 

 rocks of the district where it occurs, and from which it was derived. 

 The local glacier will alone account for the Scottish Boulder-clay, 

 while the phenomena of the English deposit requires the floating 

 iceberg. It is quite evident that the Acadian Boulder-clays agree 

 more with those of the South of England ; but while arguing for 

 their oceanic origin. Dr. Dawson must admit the local glacier origin 

 of other deposits. 



We must pass over the tempting record of the discovery of the 

 land animals of the Devonian and Carboniferous periods, and the 

 interesting account given of this singular fauna, which have been 

 imearthed first and chiefly in Acadia, and by the labours of Principal 

 Dawson ; but we must especially notice the important observations 

 he has made on the Flora of these periods. The learned author has 

 devoted his special attention to the investigation of this vegetation 

 which has left so large a record in the earth's crust. He has greatly 

 added to the number of known species, he has examined into the 

 conditions of the accumulation of coal, and determined the various 

 microscopic structures which are met with in the coal itself. And 

 now he proceeds a stage further, and re-uniting the broken and 

 scattered fragments of the plants, he builds up in a series of restora- 

 tions what appears to him to have been the aspect of the living 

 plant. In the animal kingdom the work of restoration depends more 

 on observation than on imagination, as the different parts of an 

 organism bear a tolerably definite proportion and relation to each 

 other ; but in the vegetable kingdom, on the other hand, imagina- 

 tion must be the chief source of restoration where the preserved 

 materials are few and imperfect, as no relationship exists between 

 the size of the fruit, the flower, or the leaf, and the branch, the 

 trunk, or the root. A careful comparison of the various organisms 



