440 
CAPE OF GOOD HOPE. 
Robben’s Island, on whose shore we saw, as usual, the breaking surf 
curiously refracted. 
Robben’s Island is now used as a place of confinement for criminals, 
who are employed in the quarries to furnish stone for paving and 
building. The stone is a schistus, and commonly known at the Cape 
as blue flag. 
As we cleared the island, objects to seaward were seen refracted in 
a manner that I had never before observed so distinctly. As before 
stated, there was an upper and an under current in the atmosphere, 
and these strata were of different temperature. The thermometer at 
the masthead marking 73°, while that on the deck stood at no more 
than 59°. A ship about three miles distant in the offing, was seen 
vertically and horizontally refracted at the same time. Her courses 
and topsails appeared ill-defined, shapeless, and quivering; her bow¬ 
sprit and head-spars formed curves, while her jib and flying-jib were 
drawn out in nearly horizontal lines. Above, her topgallant-sails and 
royals were seen perfectly well defined; a distinct line of bluish haze 
divided them from the lower sails, and could be traced to about sixty 
degrees on each side, until it joined with the horizon. 
A signal made by this ship at the time, showed in faint colours, as 
if flying from her peak and fore-topsail- 
yard at the same time. The annexed 
wood-cut, from a sketch made at the time, 
will give a better idea of this appearance. 
The angle subtended between the line 
of haze and the horizon, was twenty-five 
minutes. 
The temperature of the water was often tried: it was found to stand 
at about the same temperature as when we entered on soundings, 
varying little from 64°. After running off about thirty miles from the 
coast, the temperature of the air rose to the same point. 
On the 19th, Joseph Sylva (boy), died of phthisis. He had been 
long lingering, and was apparently affected with the disease when 
taken on board at Oahu, a few months previously. 
We now shaped our course for St. Helena, which I was desirous of 
reaching at the earliest day, in order to intercept the two brigs, and if 
a further supply of bread could be obtained there, to proceed with them 
directly for the United States. 
Our passage to St. Helena was of the ordinary length, thirteen days; 
we had very light winds and a smooth sea, indicating that a long calm 
had existed. Northerly currents generally prevailed, though at times 
