583 
of Edinburgh , Session 1868-69. 
I. Freshly Burned Platinum Plates. 
No. of Grove’s cells in de- ) 9 ^ 
composing battery, . . . ) 
Resulting polarisation, . . 164 1‘98 2 01 2 12 2'30 
II. Platinum + , Palladium - . 
Cells, ........ 1 2 4 
Polarisation, 1*50 P82 1'85 
III. Palladium + , Platinum - . 
Cells, ........ 1 2 4 
Polarisation, 1*60 1*92 1*91 (?) 
IV. With Three Cells. 
Platinum + , Iron — . 
Polarisation, . 2T6 
Platinum - , Iron + 
o-o 
Iron Plates. 
O'O 
V. Aluminium Plates. 
Cells, .... 1 2 3 4 6 
Polarisation, . . P09 2T7 2-44 (?) 4 - 01 5‘20 
The last results are very remarkable, showing, as they do, from 
aluminium electrodes a reverse electromotive force of more than 
five Daniell’s when six Grove’s are in circuit. The polarisation 
alters so rapidly during the electrolysis (in the case of alumi- 
nium) that I cannot be certain that the numbers above given 
represent fully the maximum effect. Various other combinations 
have been tried, but are being repeated by Mr Dewar. 
3. On the Causes of Yolcanic Action. By Joseph John 
Murphy, Esq. Communicated by Dr Wyville Thomson. 
In offering these remarks on the causes of volcanic action, I 
take it as proved that volcanoes are in communication with a 
reservoir of heat, occupying the centre of the earth : which heat, 
however, the earth is gradually, though very slowly, losing; partly 
by volcanic eruptions, partly by hot springs, and partly by the 
slow conduction of heat towards the surface through the strata. 
I also take it as proved, that the earth is not fluid but solid 
4 G 
VOL. VI. 
