Intelligence and Miscellaneous Articles. 555 



2. " On the Geology of the Upper Part of the Valley of the 

 Teign, Devonshire." By G. Wareing Ormerod, Esq., M.A., F.G.S. 



The district noticed in this paper lies to the north of Bovey 

 Tracey. The author "described the courses of the Teign and its 

 feeders, and the strata traversed by those streams — namely, Granite 

 and Carboniferous Limestone. Gravels are occasionally found, 

 which the author regarded as having been deposited before the 

 reexcavation of the valley, and he showed that these had been 

 transported by a current from north-west to south-east. From the 

 absence of these gravels in the gorge of the Carboniferous rocks 

 between Hunts Tor, near Chagford, and Clifford Bridge, he con- 

 sidered that that valley had been opened since the time when the 

 boulders and gravels were deposited, and then showed that the 

 stream from the valley of the Teign prior to the opening of that 

 valley would have passed by Moreton Hampstead to Bovey Tracey. 

 The paper contained notices of the Minerals found in the district, 

 and of the Granite veins in the Carboniferous rocks. 



3. " Notes on the Geological features of Mauritius." By George 

 Clark, Esq. 



Mr. Clark described the occurrence of a calcareous formation of 

 at least 30 feet in thickness, with a dip of about 30°, composing 

 many of the islets supported by the coral reefs of the Mauritius, 

 which have been generally regarded as forming an integral part of 

 the islets, but which the author considered to be of greater anti- 

 quity. A soft sandstone was stated to cover in many places the 

 calcareous rock, and to contain imbedded remains of roots, and bases 

 of trunks of trees. 



LXX. Intelligence and Miscellaneous Articles. 



ON THE RELATIONS EXISTING BETWEEN THE COMPOSITION, 

 DENSITY, AND REFRACTING-POWER OE SALINE SOLUTIONS. 

 BY M. FOUQUE. 



rriHE research of which the following is a succinct summary was 

 •*- made at the Imperial Observatory of Paris by the aid of instru- 

 ments belonging to that establishment, the use of which was kindly 

 granted to me by the Director. 



The object of the research was (1) to ascertain whether Biot and 

 Arago's law for gaseous mixtures also held good for saline solutions, 

 and (2) to study the variation of the refractive index, and of the 

 refracting-power, with the temperature. 



These investigations required the following operations : — (1) esti- 

 mation of the solutions ; (2) determination of their densities ; (3) 

 measurement of their refractive indices. 



The salts used, forty-three in number, were purified by the 

 ordinary chemical methods, and according to their alterability by 



