J, D. Dana— Chhritic formation west of New Eaven, Conn. 119 



ei-al smaller side-products. The known symmetry of structure 

 of tlie molecules of all these side products, however, certainly 

 argues in favor of a similar symmetry in the glyceric acid 

 molecule. 



There is one way of reconciling these two views of the struc- 

 ture of glyceric acid, and that is the assumption of the exist- 

 ence of two isomeric acids, of which one is normal and the 

 other an unsymmetrical acid. 



Some results that I have just obtained in purifying the cal- 

 cium glycerate seem, indeed, to point this way. Should the 

 unsymmetrical glyceric acid preponderate in this mixture, 

 Wislicenus' reactions with hydrogen iodide are readily under- 

 stood. Another fact, which should not be lost sight of, is that 

 in the decomposition of /i iodo-propionic acid by moist silver 

 oxide, Wislicenus* obtained not hydracrylic acid alone, but 

 three other products accompanying it, so that the decomposition 

 was not so simple 



I am now engaged upon a study of this question, and hope 

 to be able to give more information upon it in a short time. 



Art. Xll.—Note on the ''Chhritic forviation'' on the western 

 border of the New Haven Region ; by James D. Dana. 



The rocks of the hilly region west of the New Haven plain 

 are, for nine miles westward, metamorphic slates, and beyond 

 this distance mostly gneiss. Immediately adjoining the region 

 there is what Percival has called a "chloritic formation," the 

 area trending about north-northeast ; then on the west of this, 

 with the same trend, (2) a hydromica vslate, but little removed 

 from argillite, becoming slightly garnetiferous toward the west- 

 ern limit ; next (8) a glossy garnetiferous mica slate, containing 

 some beds of gray semi-crystalline limestone; next (4) at Derby, 

 common gneiss and coarse porphyritic gneiss. These rocks are 

 involved in one system of folds, and are throughout conforma- 

 ble in bedding. 



The rock of the ''chloritic formation" varies much in texture 

 and composition in passing from the Sound northward. Near 

 Savin Rock, on the Sound, it is a chloritic hydromica slate. 

 The gray and slightly silvery surface is more or less blotched 

 and lined with the olive-green of chlorite, and the rock has in 

 the mass in general a greenish tint. The slaty structure is 

 usually perfect, and yet some layers fail of it. Grains of mag- 

 netite are 3ommon, and, less so, those of pyrite. 

 * Ann. der Oh. und Ph., clxvii, p. 41. 



