430 



THE POPULAR SCIEXCE MONTHLY 



launching of some canoes, on which the na- 

 tives had been working for a long time. 

 One of the party, during the feast, drew a 

 number of figures resembling those M. Ma- 

 clay had seen, and evidently referring to 

 the work in hand. The two boats were 

 represented as they were, half on land and 

 half in water ; then followed representations 

 of men carrying pigs, the " covers " of the 

 feast, M. Maclay's canoe with its flag, and 

 the canoes of the visiting guests. Further 

 evidence has made it tolerably clear that 

 such representations are real ideographs. 

 The carvings on wood, to which a religious 

 bearing is ascribed, seem to show a regular 

 progress toward sculpture, by the transfor- 

 mation of simple decorations into bas-relief, 

 then into alio rilievo^ and finally into the 

 complete figure. 



Plant-Migrations. -An interesting mon- 

 ograph has been published at the Univer- 

 sity of Giessen, Germany, on the migra- 

 tions of two plants, the Puccinea malvacea- 

 riim, or mallows fungus, and the- Elodea 

 Canadensis {Anacharis Canadensis^ Gray). 

 The former plant was first noticed infest- 

 ing the mallows-plants of Chili. It was ob- 

 served in Spain, for the first time in Europe, 

 in 1869, having, it is thought, been intro- 

 duced in the course of trade. Next it was 

 found in France, infesting some ten species 

 of the mallows family, in 1872, 1873, and 

 1874; it appeared in England in 1873, and 

 was carried to Holland and Belgium in 

 1874. It was also found at the Cape of 

 Good Hope and in Australia in 1874. It 

 began to attract attention in Germany and 

 Italy in 1874, and appears now to be dif- 

 fused all over Europe, as its presence is 

 mentioned in Bohemia and Hungary and at 

 Athens, which appears so far to mark its 

 southeastern point of extension. The Elo- 

 dea^ or Anacharis Canadensis, was noticed 

 in single localities in Ireland in 1836 and 

 1842. Toward 1850 it became quite abun- 

 dant, and in the course of the next ten 

 years found its way to the Botanical Gar- 

 dens of Utrecht and the swamps in the 

 neighborhood of Ghent. It was growing in 

 several places in France in 1866. It is now 

 found in considerable abundance in the 

 lower Rhine, the Elbe and its branches, the 

 Havel and Spree, and the Oder. It has ex- 



tended from Corrib, Ireland, on the west, 

 and Grenoble, France, on the south, to Riga, 

 on the northeast. It has been carried by 

 sprouts to all the places where it grows ; 

 for only female plants (not a single male 

 plant) are to be found in all Europe. 



Efficiency of Present Causes in Geologi- 

 cal Action. M. Stanislas Meunier has re- 

 cently published a work discussing the suf- 

 ficiency of the causes which are still in 

 operation to account for the production of 

 the geological phenomena of the past. Il- 

 lustrations of the principle involved in the 

 discussion may easily be found in examin- 

 ing some of the formations near the sur- 

 face. In the section of the coal-beds of 

 Valenciennes, thick, horizontal cretaceous 

 beds appear, resting on carboniferous beds, 

 the strata of which are contorted, bent, and 

 folded neither more nor less than the strata 

 of which the highest mountain-chains are 

 composed. As the contact of the chalk and 

 the coal is horizontal, it must be admitted 

 that, previous to the deposit of the second- 

 ary rocks, the ground, which had been 

 greatly disturbed by the foldings of the 

 carboniferous strata, had been again planed 

 down to a level. The first thought would 

 be to attribute the planing down to some 

 sudden and violent action carrymg away all 

 of the missing matter at once. The view is 

 entirely changed when we remark that quite 

 as important denudations are taking place 

 now in populous districts without any per- 

 turbations of a violent character. Thus, on 

 the British coast of the English Channel 

 the sea is gaining about a yard a year upon 

 the land, and the fact is recognized in sales. 

 The result of this denudation, which is tak- 

 ing place so gradually, can not be distin- 

 guished from that of a sudden razing of the 

 strata at the bottom of the sea. M. Meunicr 

 examines likewise the theory that river-val- 

 leys have been formed by the action of 

 streams in a period of floods, when they 

 were many times larger than the present 

 rivers. The valleys of the rivers, he be- 

 lieves, correspond with original fractures of 

 the soil ; this once accepted, we may admit 

 that the stream was neither much more vo- 

 luminous nor much more rapid in quaternary 

 times than at present. In the course of an 

 indeterminate period of time it has widened 



