172 Scientific Intelligence. 



minerals were found for the first time in Maryland in May, 1895,. 

 in a pegmatite dike, in the quarry of hornblende schist operated 

 by Alphaeus H. Wright on Stony Run, east of Hampden. The 

 gangue is white feldspar (oligoclase) together with mica, com- 

 pact garnets in mass, talc, etc. They occur in the cracks and 

 veins of the oligoclase as thin crusts, mostly in radiated crystals, 

 isomorphous with epidote, with which it is intimately associated. 

 The epidote has a brighter luster than the Jones Falls specimens 

 in general. 



The thulite is bright pink, shading off into light pink and light 

 orange, clear and glassy. The crystalline form of the zoisite is 

 identical with that of the thulite. It is gray, shading into the 

 light and dark green' of the epidote. There is room for question 

 whether this should not also be regarded as thulite. Foliated, 

 stellated and granular talc also occur, occasionally changing to 

 deweylite. Bright iron pyrites is also often met with. The 

 quartz has yielded a single crystal of beryl of good size and 

 color — a rarity in Maryland. 



Harris gneiss quarry on Jones Falls has yielded a large quan- 

 tity of epidote but all of one color — dark bottle-green, but the 

 slightest tint of pink or gray or intermediate colors has never 

 appeared here, though the two localities are scarcely half a mile 

 apart. 



III. Miscellaneous Scientific Intelligence. 



• 1. The Transcontinental Triangulation and the American 

 Arc of the Parallel ; by Chas. A. Schott, Chief of the Comput- 

 ing Division. Pp. 871, with 2 maps and 55 illustrations; 4to. 

 Washington, 1900. (United States Coast and Geodetic Survey, 

 Henry S. Pritchett, Superintendent. General Publication, No. 

 4). — The work of transcontinental triangulation began in 1871. 

 Its completion in 1900 "marks an epoch not only in the scientific 

 history of the United States but in the world's Geodesy as well." 

 We have now a continuous triangulation along the 39th parallel 

 from the Atlantic to the Pacific 2,025 miles in length. Its value 

 to the sixteen states embraced by it need not be explained. Its 

 value from a scientific standpoint consists in the great addition it 

 offers to the data necessary for the accurate determination of the 

 earth's shape and size. No contribution to geodesy of equal 

 magnitude has ever been made, that most nearly comparable 

 being the measurement of the great Indian arc. 



Its main result may be summarized in the statement that the 

 curvature of the North American continent along the 39th paral- 

 lel given by it is intermediate between that of the Bessel and 

 the Clarke spheroids. The accuracy of this deduction is evi- 

 denced by the fact that the probable error in the measured length 

 of the entire arc of 4,224 kilometers is 26 meters, while the dif- 

 ference on the spheroids of Clarke and Bessel for the same arc is 

 615 meters. 



