May 21, 1897.] 



SCIENCE. 



811 



stroyed a few seasons ago by a combination of 

 strong winds and heavy snowfall, followed by 

 cold, the result being that exceptionally low 

 water was produced, ice formed on the exposed 

 flats, and when the tide finally came in the 

 plants were torn away and carried oflF. Mr. 

 Ooville noted the conditions under which the 

 shallow water could be restocked with the wild 

 ■celery, and stated that it had been successfully 

 transplanted to Western lakes, with the desired 

 result of causing the canvas backs to linger 

 there on their migrations. 



Mr. Coville also described ' The Water Hya- 

 cinth, Piaropun crassijjes, as an obstruction to 

 navigation in Florida,' saying that in some of 

 the shallow rivers the accumulation of the 

 plants impeded the progress of the steamers. 

 He showed a view of steamers so surrounded by 

 the water hyacinth that they appeared to be 

 lying in a meadow, and described the experi- 

 ments made with a view to the possibility of de- 

 stroying the plants. 



Mr. Lyster H. Dewey described ' The Eastern 

 Migration of Certain Weeds in America,' saying 

 that the general trend of weed migration in the 

 States east of the Kocky mountains, except in 

 New England, has been westward, correspond- 

 ing with the direction of the progress of cultiva- 

 tion and the movement of the supply of field 

 seeds. In New England weeds have spread to 

 the eastward, as illustrated by the Canada 

 Thistle, Carduus arvensis, and the Orange hawk- 

 weed, Sieracium atirantiacum, introduced into 

 Vermont and New York, and spreading from 

 these States eastward. Yellow daisy, Budbeckia 

 hirta; bracted plantain, Plantago aristata; low 

 amai-anth, Amaranthus blitoides ; marsh elder, 

 Iva xanthifoUa; buflalo bur, Solanum rostrafum ; 

 squirrel tail, Hordeum jubatum, and Russian 

 Thistle, Salsola kali tragus, are given as instances 

 of weeds that have spread to the eastward. 

 While the westward migration of weeds has 

 been largely through impure field seeds, the 

 eastward movement appears to be chiefly along 

 railroads, in baled hay, grain and wool. 



277TH MEETING, SATURDAY, MAY 8 . 



The entire evening was devoted to the pres- 

 entation and discussion of a paper by Dr. C. 

 Hart Merriam, on ' Suggestions for a New 



Method of Weighing Species and Subspecies, ' 

 which appeared in the last issue of Science. 

 F. A. Lucas, 



Secretary. 



geological society of WASHINGTON. 



At the regular meeting of April 14, 1897, 

 Mr. H. W. Turner read a paper on ' A new 

 Amphibole-pyroxene rock and some Orbicular 

 rocks from California.' 



The new amphibole-pyroxene rocks consists 

 of original augite and amphibole in grains, of 

 nearly equal size, with a little quartz and some 

 pyrrhotite. The rock contains numerous phen- 

 ocrysts of brown amphibole, which contain in 

 a poikilitic manner the constituents of the 

 ground mass. This rock is one type of a very 

 interesting series of basic igneous rocks found 

 in the foot hills of Mariposa county, Califoi'nia. 



Some orbicular rocks were exhibited, as well 

 as an inclusion in granite, around which an 

 aureole, composed of amphibole, had formed. 

 The material of this aureole appears to have 

 been segregated from the granite. Two speci- 

 mens of dikes were exhibited, the center of 

 each of which contained more silica than the 

 borders. Reference was also made to dikes in 

 the rainy lake region, shown by Lawson to 

 have an interior portion more siliceous than the 

 borders. It is well known, as a general rule, 

 that the less siliceous elements crystallize out 

 first in all rock magmas. The walls of the dike 

 being cooler, the less siliceous minerals would 

 crystallize out first along the border, and the 

 more acid minerals be transferred by convection 

 currents, or in part crowded out by the already 

 crystallized material toward the interior. It is 

 evident that along the borders of an intrusive 

 area of great size the same phenomenon might 

 be shown. We should simply have the case of 

 one side of the dike. The laws of thermo- 

 chemistry would appear to be applicable to 

 this case, inasmuch as the heat generated by 

 the crystallization of the minerals might aid in 

 establishing convection currents to transport the 

 residual siliceous constituents away from the 

 already consolidated material. 



Under the title ' Laccoliths in Folded Strata,' 

 Mr. W. H. Weed described the occurrence of a 

 number of lenticular masses of intrusive rock 



