scientific Intelligence. -^Geology. 187 



norant of. The petrosilex of Sahlberg, not only does not be- 

 long to compact felspar, but constitutes a new species, composed 

 of silica, alumina, soda, and magnesia. — Btdlet. Univ. Aout 

 1827. 



GEOLOGY. 



is. Frmn what Countries Imve the Islands in the West In- 

 dies derived their Plants ? — M. Moreau de Jonnes, who sup- 

 poses that the deposits, whether calcareous or volcanic, of tlie 

 Antilles, have been left dry by the sea at a later period than 

 the great continents, had, in support of this opinion, to inquire 

 into the origin of their vegetable population, and to endeavour 

 to find out by what agents, and from what countries, each of 

 their plants, was transported to them. For this purpose he 

 prepared, during his residence at Martinique, mixtures of earth 

 adapted for vegetation, and in which, he was well assured, there 

 existed no germs of plants. He exposed them with the requi- 

 site precautions, and separately, to the action of tempestuous 

 rains, to that of different winds, of birds of passage, and of va- 

 rious currents, and counted, as far as was possible, the number 

 of species which each of these causes produced. He also en- 

 deavoured to estimate how far man himself may contribute to 

 this end, by transporting seeds or germs of plants in the water 

 brought from other countries in ships for the use of their crews, 

 among the matters used for packing foreign goods, among wood 

 and fodder, as well as in ballast, and among the hair of animals. 

 The most powerful and constant of the natural agents appears 

 to him to be the great equatorial current of the Atlantic. He 

 found that, in the space of two months, it brought seeds of 150 

 different species ; but all seeds are not capable of being equally 

 transported by all the agents, and to be able to arrive at a given 

 distance in a condition to reproduce their species, they require 

 to possess certain conditions of lightness, mobility, resistance to 

 destruction, difficulty or facility of germination, and others of a 

 like nature. Thus, among the 150 species of seeds brought by 

 the current, there were only twenty-six that germinated. With 

 regard to the action of man, M. de Jonnes thinks it much su- 

 |)erior to that of natural agents, and im'agines that, in a few 



