January 15, 1897.] 



SCIENCE. 



97 



stone. He also spoke of the enrichment of 

 metamorpliic rocks in the Hoosick region 

 with albite, and therefore with soda, necessi- 

 tating caution in the interpretation of analy- 

 sis. Mr. Adams, in reply, described the Gren- 

 ville series as made up of closely involved 

 limestones and gneisses, the latter exactly 

 like the fandamental ones. He stated that 

 pegmatite dikes cut the limestones in every 

 direction. He also said that his analyses, 

 on which the conclusions regarding the 

 sedimentary origin of certain of the later 

 gneisses were based, had shown such low 

 alkalies and high alumina as to warrant it. 

 There could, therefore, have been no enrich- 

 ment with soda. Mr. Cross cited, in com- 

 parison, the granites and gneisses of the 

 Rocky Mountains. Mr. Iddings questioned 

 the fact of the fundamental gneisses being 

 the original crust. Dr. Adams replied urg- 

 ing its world-wide extent and fairly uniform 

 acid character despite some more basic 

 members. Prof. Emerson remarked on the 

 distinction that was made between intruded 

 fundamental gneiss regarded as older than 

 the limestones and intruded lavas that 

 would be called later. He raised the point 

 that both were practically the same and 

 that if an intruded lava were called a later 

 rock, although it had existed in the interior, 

 perhaps from very early time, then gneisses 

 now found intruded should also be regarded 

 as later. Dr. Adams, in reply, urged the 

 conception of the original crust, and in- 

 sisted that, even if after the Grenville-Hast- 

 ings series had been laid down on it the 

 great batholite softened and penetrated 

 them, it was still to be considered older. 

 The section evidently held diverging views 

 on this point. 



The Crystalline and Metamorphic Books of 

 Northwest Georgia. C.Willaed Hayes and 

 Alfred H. Brooks, Washington, D. C. 

 The region discussed in the paper extends 



southward one hundred miles from the 



Tennessee line and westward twenty to 

 eighty miles from the Atlanta meridian. 

 It embraces about 4,000 square miles, form- 

 ing a belt to the east and south of the 

 Georgia-Alabama Paleozoic area. The 

 rocks described consist of (1) the slates 

 and conglomerates of the Ocoee series, (2) 

 the granites, gneiss and crystalline schists 

 of the Piedmont basal complex, and (3) a 

 series of intrusives including granite, 

 diorite, gabbro. 



By means of maps colored to show the 

 distribution of the rocks, their areal rela- 

 tions were outlined and many interesting 

 points were adduced, not the least of which 

 were those connected with the intrusive 

 granites, so prominent east of Atlanta at 

 Stone Mountain. 



Dr. A. C. Lane asked about the intruded 

 rocks and if there were contact zones. Mr. 

 Brooks replied that there were zones of 

 ottrelite and andalusite schist around both 

 granites and diorites. Mr. Keith also 

 inquired about certain stratigraphical rela- 

 tions. 



The Grain of Rocks. Alfred C. Lane, 



Houghton, Mich. 



The grain of rocks is dependent on the 

 chemical composition and the causes that 

 produce solidification, cooling, gas diffusion, 

 etc., the general law being, the more rapid 

 the action the finer the grain. The paper 

 discussed the grain from the threefold stand- 

 point of theory , observation upon the Kewee- 

 nawan rocks and experiment. 



In regard to chemical composition, the 

 augite of the melaphyres shows plainly the 

 empirical law that the less there is of it 

 the finer is the grain, other things being 

 equal. 



The mathematical laws of cooling were 

 applied to an indefinite sheet and the fol- 

 lowing laws deduced and tested: 



(a) Tlie case where we consider the ad- 

 jacent rock symmetrically heated by the 



