506 Transactions.— Geology. 
Analysis of the Slate. 
Moisture driven off at 105? C. e. *» ds 2 -475 
* Water lost at a rel heat os oe ve <i ee 
Silica s5 oe ae E ae .. 52°259 
Alumina T oe .. s s 2 401724 
Tron sesquioxide ve e» ae ae 29207 
» protoxide .. os 6 $s e , 40094 
Phosphoric acid. . € .. še s .. absent 
Manganese protoxide — .. e . xa SNP rii 
i v» as +e is Y» .. 9:984 
i zx ss e x s. 199 
Potash M > E ap a zc. 054 
Soda .. = ee ws XE er c qua 
Carbonic acid .. ye 4a os ee +. - traces 
100-237 
Specific gravity = 2°713. ur x 
It will be at once observed that there is far less silica in the slaty portion 
than in the granitie, and that the bases have undergone a corresponding 
increase in their amounts; this is most noticeable in the percentage of iron, 
alumina, manganese, and magnesia. The increase in the proportions of the 
bases present has been accompanied by a rise in the specifie gravity of the 
slaty portion. 
Note.—This specimen was obtained by myself in Isthmus Sound, Preservation 
Inlet. See“ Geology of Otago," Dunedin, 1875, p. 40.—F. W. H. 
* This was estimated by direct weighing in a calcium chloride drying-tube. 
