1892.] NEW YORK ACADEMY OF SCIENCES. 65 



and referred to this cause rather than to pressure. A deep reddish- 

 brown biotite is also occasionally present, but is far more abundant 

 toward the south of this upper third of the dike. Its colors are 

 those of the biotite commonly seen in nepheline rocks, but it has a 

 well-marked diver^-ence of the optic axes. It affords an excellent 

 percussion (schla^) fif>-ure, and the plane of the optic axis is parallel 

 to the principal ray (010), proving- it a mica of the second order, 

 as is to be expected. It occurs in irreg-ular shreds, and is older 

 than the aeg-irine. The most micaceous normal sj^enite is a short 

 distance south of Thomas Conway's house. Titanite is usually 

 present, and from decomposed syenite small crystals (0.5 mm.) can 

 be picked out which show good faces. The}^ are honey-yellow 

 in color. Professor Rosenbusch, to whom I have sent a suite of 

 specimens and with whom I have had some correspondence, re- 

 marks the passage of the titanite into bordering rutile nets. He 

 also has noted the occasional presence of fluorite, which has escaped 

 my notice. Small amounts of magnetite are generally seen, and 

 pyrite is common. 



A partial analysis (I.) of number 34, which was collected as nearly 

 as I could determine from the point visited by Professor Emerson, 

 was kindly made by Mr. F. W. Love, of Cornell University. The 

 complete results were not obtained in time to insert, but will be dis- 

 tributed in the reprints. Column II is the ditroite of Hungary 

 (Feliner, Verb. d. k. k. Geol. Reichsanstalt, 1867, 286, quoted by 

 Rosenbusch, Tsch. Mitth., xi, 144, Taf. 1). Column III is the 

 elaeolite-syenite of Brazil (Machado, Tsch. Mitth., ix, 334). Col- 

 umn IV. is the elaeolite-syenite of Arkansas (J. F. Williams, 

 Jf^neous Rocks of Ark., p. 81). Column V is the Norwegian 

 elaeolite-syenite (Brog-ger, Syenitpegraatitgiinge, p. 33). 



100.9 99.70 99.56 99.82 



It thus appears that the Beemerville rock is rather basic in its 

 chemical composition. Several pounds of the rock were crushed 

 fine and panned for small minerals of high specific gravity, but only 

 aegirine, titanite, magnetite, and a little apatite resulted. Emerson 

 found a variety that was nearly pure elaeoli c, and much the same 

 has been met by me along the contact just above Thou)as Conway's 

 house. The rock is very finely crystalline and contains wavy lines 

 of aeij-irine and biotite, due to flow structure. The biotite, at times, 



