752 



SCIENCE. 



[N. S. Vol. III. No. 72. 



velopment of the aptychus was initiated in the 

 earliest shelled condition. The affinities be- 

 tween the Ammonites and Dibranchiates were 

 shown to be on the whole very close, yet the 

 evidence furnished by their internal structure 

 and shell development is so strongly in favor of 

 the Tetrabranchiate character of Ammonites 

 that their separation from the Nautiloids seems 

 at present unwarranted. 



The Quartz Porphyry and Associated Socks of 

 Pequatuket Mountain (the eastern ' Kearsarge ' 

 of New Hampshire). By R. A. Daly. 

 Both of the geological surveys of New Hamp- 

 shire noted the presence of the remarkable flow 

 breccia outcropping on what was long called 

 ' Pequawket Mountain.' The second survey 

 placed it in their table of formations under the 

 name of the ' Peciuawtet Breccia. ' The moun- 

 tain is chiefly composed of a typical quartz por- 

 phyry in which inclusions of various rocks lie 

 embedded. The object of this paper was pri- 

 marily to present the results of an examination 

 of a large number of microscopic slides prepared 

 with the purpose of tracing the extent to which 

 the inclusions had sufiered from the metamor- 

 phism of the igneous body. The great slate 

 mass on the south side of Kearsarge, is a gi- 

 gantic horse in the poryhyry. It is about four 

 hundred yards long from east to west and one 

 hundred and fifty wide and lies close against 

 the contact of the older ' Albany Granite. ' On 

 the border of the slate, severe brecciation has 

 been produced, some phases being composed 

 entirely of aggregated slate fragments, others 

 with a variable proportion of quartz porphyry 

 cement. Throughout the mountain small in- 

 clusions of the same phyllitic slate, from two 

 feet to a fraction of an inch in diameter, are ex- 

 ceedingly numerous. Now, the striking fact in 

 connection with them is the almost absolute 

 lack of metamorphic change which has affected 

 these fragments. The great horse of the south 

 side does not betray any marginal alteration, 

 except in the physical way already noted. This 

 is a marked exception to the general conclusion 

 of Lacroix that chemical rearrangement is usual 

 in bodies enclosed within volcanic rocks of his 

 ' trachytoide ' type. (Mem. de 1' institut de 

 France t. XXXI., 1894, p. 81.) Itisall themore 



remarkable on account of the fact that the field- 

 evidence shows the porphyry to be not a 

 surface flow, but the filling of a neck where we 

 should expect high temperatures and pressures 

 and the presence of mineralizers to have pro- 

 duced extensive alteration. 



The contemporaneous porphyry of Moat 

 Mountain is in a similar tectonic relation and is 

 likewise filled with inclusions of the same gen- 

 eral nature as those of Kearsarge. Here also 

 the metamorphism is almost nil. It is of inter- 

 est to note that the base is not vitro-phyric as 

 in the Kearsarge rock, but granophyric with 

 accessory crystalline ingredients. Besides the 

 phenocrystic quartzes and microperthitic feld- 

 spars, the rock is composed of a dense micro- 

 granitic matrix of quartz and feldspar, with 

 abundant minute grains of hornblende, titanite, 

 zircon, apatite and primary fiuorite. This com- 

 position allies the rock closely to the ' Albany 

 Granite,' which is, in part, the country rock of 

 these porphyries. 



The eruptions occurred after the last im- 

 portant White Mountain uplift. The eruptives 

 are not squeezed, and their inclusions are, in 

 part, derived from the crystalline schists, of 

 the Montalban terranes. The slates, sand- 

 stones and phyllites probably represent masses 

 which have sunk to their present level in the 

 vent from the superficial zone of minimum 

 metamorphism during the mountain building. 

 It is, however, conceivable that they might 

 have been carried up from a zone which lay be- 

 low the level of no strain at the time of plica- 

 tion. 



T. A. Jaggar, Jr., 

 Recording Secretafy. 



PHILOSOPHICAL SOCIETY OF WASHINGTON. 



At the regular meeting, on April 2.5th, the 

 following papers were presented, both being ex- 

 tensively illustrated with photographs of build- 

 ings in various parts of the world and plans and 

 designs for the Capitol and Executive Mansion 

 ia Washington, the one by Wm. Martin Aiken 

 on the ' Influence of Climate on Architecture,' 

 and the other by Mr. Glenn Brown on ' Early 

 Government Architecture.' 



Bernard R. Green, 



Secretary. 



