Volcanic Rocks in Maine.— In a preliminary notice on the rocks 

 of the Flox Islands, Maine, G. O. Smith* gives a brief account of the 

 association of lavas and breccias on North Haven and Vinal Haven 

 Islands. On North Haven the series consists of beds of porphyrites 

 and of coarse volcanic breccias and conglomerates, layers of tuffs and 

 sheets of quartz-porphyry. The porphyrites are sometimes olivinitic. 

 The conglomerates and breccias are composed of fragments of the por- 

 phyrites cemented by a porphyritic matrix. The quartz- porphyry pos- 

 sesses no unusual features. On Vinal Haven the rocks are predomi- 

 nantly acid, comprising many banded and spherulitic felsites that were 

 originally glassy rocks. The spherulites are felsitic or fibrous and are 

 certainly original structures, since transitions from the felsitic into 

 brecciated rocks may be traced, in the latter of which occur spherulites 

 that were formed prior to the brecciation. The acid layers of the 

 series are younger than the basic beds. 



Spotted Quartzites, S. Dakota.— The Sioux quartzites in Min- 

 nehaha Co., S. Dakota, grade upward into variously colored quartz 

 slates that are composed of quartz grains, iron oxides and mica in an 

 argillaceous matrix that has crystallized in part as sericite, kaolin and 

 chlorite. Many of the slates are marked by spots that are lighter than 

 the body of the rocks. These spots are essentially of the same compo- 

 sition as the groundmass in which they lie, except that they contain 

 less iron oxide. Their lighter color is due to bleaching out of the iron 

 salt through the acid, probably of decomposing organic matter/* 



The Gneisses and 'Leopard Rock' of Ontario. — The gneisses 

 interstratified with the limestones in the Grenville series, north of 

 Ottawa, Canada, vary much in character. 6 The predominant variety 

 is a granitoid aggregate of reddish orthoclase and grayish-white quartz, 

 a little or no mica, and sometimes garnets. Its bedding is very obscure. 

 When the mica is abundant in the rock foliation is distinct. One 

 variety of the rock is called by Gordon syenite-gneiss. It includes 

 the ' leopard rock ' of the Canadian geologists. The rock occurs as 

 dykes cutting quartzites and pyroxenites. All the phases of the 

 gneisses show the effects of pressure. The ' leopard rock ' consists of 



* Johns Hopkins Univ. Circulars, No. 121, p. 12. 



3 Beyer : lb., No. 121, p. 10. 



