ANNUAL OF SCIENTIFIC DISCOVERY. 



stagnant water cannot produce any trees, because the trees require 

 for their growth, like most of the terrestrial plants, the introduction 

 of atmospheric air to their roots. Neither do trees germinate and 

 grow ou a ground alternately covered with stagnant water and ex- 

 posed to dryness for some months of the year. From these consider- 

 ations, the law of the general formation of the prairies can be de- 

 duced : While a land or a part of a country is slowly passing from the 

 state of swamp or marsh to the state of dry land, the annual alterna- 

 tion of stagnant water and dryness causes the vegetation of peculiar 

 plants, which, by their decomposition, form a peculiar soil unfavora- 

 ble to the growth of the trees. From this general rule of formation, 

 which regards only the prairies of the Mississippi valley, 1 all the differ- 

 ent phenomena or peculiar appearances of the prairies can be easily 

 explained. 



CURIOUS ILLUSTRATION OF THE DEIFT AGENCY. 



At the close of a recent geological discussion at the Cooper Insti- 

 tute, New York city, Professor Mason remarked that several years since 

 he happened to have a conversation with a man who had spent his life 

 in buying and selling land, and the man told him that he very soon 

 learned not to take up land on the north side of a hill. Professor 

 Mason said that his attention being thus called to the matter, he had 

 made very extensive observations and inquiries, which had fully con- 

 firmed the opinion of the speculator. He added, if any one who has 

 occasion to ride from New York to Canada will observe, he will see- 

 that the lands are generally cleared for cultivation upon the south 

 sides of the hills, while the forests are left standing upon the north 

 sides, which are comparatively barren ; the currents of the drift pe- 

 riod, coming from the north, and impinging directly upon the north- 

 ern slopes, having washed the soil and debris from their surfaces. 



CONTRIBUTIONS TO OUR KNOWLEDGE OF COAL. 



Prof. J. W. Dawson, of McGill College, Canada, has lately pub- 

 lished, in the Proceedings of tlte Geological Society of London, two 

 very interesting memoirs : one concerning the vegetable structure in 

 coal ; the other on a terrestrial mollusk, a Myriapod^ and some new 

 species of reptiles from the coal of Nova Scotia. 



The formation of the coal and the composition of its combustible 

 matter may be considered as settled questions. But we are still far 

 from being well acquainted with the true nature of the coal plants, 

 and with their generic and specific affinities. Fossil plants are 

 found preserved in two different ways. In the shales and the sand- 

 stones the outline of the vegetable is marked just as it would be on 

 the stone by the pencil of a lithographer, but no trace of internal 

 structure is preserved; and as these remains are mostly broken 

 parts of stems and of leaves, crushed cones, scales or blades, nutlets 

 and prints of various forms left on the bark of some trees at the 

 point of attachment of the leaves, it is nearly impossible to determine 



1 The prairies of the far West, along the eastern base of the Rocky Mountains, 

 are true saudy deserts, caused by the dryness of the atmosphere. 



