30 PASSAGE FROM MADEIRA 
afford an opportunity of settling the origin of this plant, which is 
spread over the whole ocean; but my time did not permit me to 
make this deviation from our direct course, and I hoped on my 
return to have ample leisure for its exploration. 
On the 29th of September, we passed into discoloured water, as 
green in appearance as that of fifty fathoms depth. On entering it 
the thermometer fell one and a half to two degrees. The distance 
run in it was about four hundred and fifty miles. Repeated casts of 
the deep sea lead were had in from two to three hundred fathoms, 
but no bottom found. The water was particularly examined for 
animalculse, but none were detected. On leaving it a rise of tem- 
perature took place of two degrees ; and much phosphorescence was 
seen when we had passed out of it. 
The first shoal searched for was the Maria Rock, said to be in 
latitude 19° 45' N., and longitude 20° 50' W. In its neighbourhood 
our position was carefully ascertained. The vessels were then 
spread in open order, and a course sailed to pass directly over the 
spot. The surface of the ocean visible was not less than twenty 
miles in latitude, with every opportunity which clear weather could 
afford. Good look-outs were kept at the masthead, and there was a 
sufficient swell to cause breakers on any shoal within fifteen feet of 
the surface. We ran over the locality without perceiving any thing 
that indicated a shoal. 
The situation of the Bom Felix Shoal, laid down about ten leagues 
to the south of the above, was passed over in the same manner, 
sounding repeatedly for bottom with three hundred fathoms of line, 
but no appearance of a shoal was observed. 
The reported position of the Bonetta Rocks next claimed our 
attention, in latitude 16° 32' N., and longitude 20° 57' W. After 
this locality had been well examined, a course was steered over its 
supposed bearing from Bonavista, one of the Cape de Verde Islands. 
The vessels of the squadron sounding every half hour during the 
night, which was clear and bright moonlight.* 
* Since our examination, I have seen a letter from the American consul at Porto 
Praya, F. Gardiner, Esq., detailing the wreck of the British ship Charlotte in 1841, and 
placing this shoal in latitude 16° 17' N., longitude 22° 21' W., 84' in longitude and 15' 
in latitude from the position I searched for it in j whence it appears that it is the same 
reef on which the Magdelaine was lost. I have no kind of doubt but that they ought all 
to be referred to the Hartwell Reef. The same gentleman was confident at the°time I 
saw him that the Magdelaine had been lost on the reef of that name. 
