Intelligence and Miscellaneous Articles. 153 



occurrence, as Upper Keuper Sandstone. They are underlain by- 

 sandstones. In these two upper divisions we have the continuation 

 of the whole Triassic series of the second area, and in the third 

 underlying division conglomerate and pebble- beds. Prom Watchet 

 to a point west of Wellington this division is represented by hard 

 bedded conglomerate, thence to the south coast by sands with rounded 

 grains and pebbles, at first of quartz grit and slate, gradually giving 

 place to the large foreign- derived quartzites of Budleigh Salterton. 



A second series of marls is found to underlie the conglomerate and 

 pebble-beds conformably. This attains as much as 500 feet in 

 thickness near the south coast, but in the northern part of the 

 district does not appear to exceed 200 feet. 



The base of the series is composed of sandstone, breccia, and occa- 

 sionally clays, occurring at different horizons in different parts of 

 the area, and each variety locally predominant over the others. 



The clay beds appear to be confined to the neighbourhoods of 

 Exeter and Crediton. The upper part of the division south of 

 Bradninch seems to consist of red sandstones, the lowermost and 

 principal part of the division consisting of breccia. jSTorth of Brad- 

 ninch the sandstone occupies the principal portion of the division, 

 sometimes apparently to the exclusion of the breccia. Towards 

 Wiveliscombe the upper part of the series for from 15 to 30 feet con- 

 sists of breccia and breccia-conglomerate, the major part consisting as 

 before of sandstones. North of Wiveliscombe breccia begins to pre- 

 vail, and in the Stogumber valley principally represents the division. 

 Owing to the conformity of the various members of this latter 

 group, they appear to represent continuous deposition. We might 

 fairly consider the upper marls and sandstones as representing the 

 Keuper, as their average thickness taken together can scarcely be 

 under 1000 feet. 



The lowermost sandstone and breccia may be taken as equivalents 

 of part of the Bunter, as they are probably 1000 feet thick near the 

 south coast, and 300 where least developed. 



The representation of the Muschelkalk would lie then between 

 the conglomerate and Lower Marl divisions, and the one rejected be 

 incorporated with Keuper or Bunter. 



XXI. Intelligence and Miscellaneous Articles. 



REPORT ON SOME EXPERIMENTS OF DR. E. ROOT, OF BOSTON, 

 CONCERNING THE PENETRATION OF PLATINUM BY ELECTRO- 

 LYTIC GASES. BY DR. HELMHOLTZ. 



rpHE experiments which I related to the Academy on the 21st 

 -*- July, 1873, had led me to consider that, in galvanic polarization, 

 portions of the gases, not merely adhering to the surface, but also 

 penetrating deeper into the platinum, must play a part, of which 

 the possibility had already been indicated by Graham's experiments 

 on palladium and platinum. In order to obtain a practical de- 

 monstration of the penetration of platinum by the gases in galvanic 

 polarization, I induced Dr. Elihu Root to ascertain, by experiments 



