Dr. Andrews on the Chemical Inactivity of Bismuth. 555 



removing the platinum from the liquor, the bismuth will sometimes 

 begin again to dissolve; at other times, its surface will become co- 

 vered with a black crust, which is soon removed by the acid -, but the 

 metal, though now exhibiting a beautifully-polished surface, is no 

 longer acted upon by the acid, or, at least, is dissolved only with ex- 

 treme slowness. Thus, a slip of metal, which, in its ordinary state 

 will require only a few seconds to complete its solution, will, when 

 thus slightly modified, resist for many hours the action of the same 

 acid. 



Copper and tin present similar phenomena, but zinc, when treated 

 in the same way, has its oxidation and solution not arrested, but 

 merely retarded. Arsenic was found to present a singular anomaly 

 when heated in nitric acid so as to give rise to effervescence : the 

 contact of the platinum in the usual way did not produce any effect j 

 whereas, when an acidulous solution of silver is used, platinum exer- 

 cised its usual influence. 



In the case of six metals, platinum checks the action of nitric acid, 

 and three of them appear to be brought into a permanently peculiar 

 state, opposed to chemical action. Platinum always separates any 

 film of oxide as its initial function ; but after its separation, it exer- 

 cises a polarizing action, for example, it brings the other metal into 

 a peculiar state, which enables it to resist chemical action. 



On the conclusion of this paper, the President drew the attention 

 of the Section to the analogy between the facts detailed by Dr. 

 Andrews, and the preservation of iron by brass, as instanced in 

 the communication of Mr. Hartley. In both cases, according to the 

 known laws of electro-chemical action, effects, the very opposite of 

 what are observed, should present themselves. The bismuth, copper, 

 &c, should oxidize quickest when in contact with the platinum; and if, 

 as would seem demonstrated by Mr. Hartley, brass protects wrought 

 and cast-iron, the brass itself should be acted upon with increased 

 rapidity. The solution of these anomalies, he conceived to be quite 

 within the range of science in its present state, and he urged upon the 

 members of the Section the necessity of studying the phenomena in 

 question, as their explication would constitute a very valuable addition 

 the existing state of our electrical knowledge*. 



Section of Geology and Geography, Sept. 1 2. — Mr. Horner exhi- 

 bited to the Section a drawing representing some of the Geological 

 phaenomena in the neighbourhood of Christiania, in Norway, and 

 read a letter from Mr. Lyell in explanation. This part of Europe 

 received some years ago an examination from M. von Buch, and the 

 results were at that time presented by him to the scientific world 

 in such a manner, as to excite much attention, and to stagger 

 many in their attachment to the Wernerian Theory, then very preva- 

 lent. Von Buch had discovered granite overlying fossiliferous strata 

 outstepping the bounds prescribed to it by Werner, so that his disci- 

 ples were obliged to invent a creation of it at a later date, to explain 

 the Norwegian phaenomena. Mr. Lyell has lately examined this in- 

 teresting locality, and has found the junction of the granite with the 

 * See Prof. Schcenbein's paper in the present number, p. 545. 

 4B2 



