ADMIRALTY ISLANDS. 
141 
the harbour, H.M.S. “Challenger” escaped shipwreck almost by a hair’s-breadth. A patch of 
coral reef not more than a few yards square, and which had escaped our attention at the 
time of entering the harbour in the dusk of the evening, was discovered right in our track, 
and as the ship was under steam, although moving slowly, it was too late to avoid it. Its 
depth below the surface proved to be only three and a-half fathoms, little more than the 
draught of our ship when not heavily laden. Fortunately we cleared the dangerous rock, 
with the assistance, as it appeared at the critical moment, of a friendly wave which lifted us 
over. There seemed 
to be shallow water to 
the eastward of the 
rock, which has been 
called the “ Challenger 
Shoal,” so that the entrance to Nares Harbour is in the channel between the latter and 
Observation Island, a low patch above water covered with a few trees, and forming the 
eastern end of the great D’Entrecasteaux Reef. The depth in this channel, as well as in 
Nares Harbour, is from twenty to forty fathoms. Still anxious to trade, our dusky friends 
had followed us out of the harbour, one of them holding up a large carved wooden bowl; 
but with the rapidly setting sun we soon lost sight of each other. 
Our cruise from the Admiralty Islands to Japan, a distance of about 2500 nautical miles, 
occupied more than a month, and was rendered very trying, both to our temper and our health, 
by the great heat which prevailed most of the time, the frequent calms, and the baffling winds 
which kept us at a distance from islands we hoped to see and perhaps explore. We had 
intended, if possible, to examine, on Tinian, one of the Mariana Islands, the remarkable 
ancient monuments, the presence of which in this remote part of Polynesia has created much 
interest among archaeologists. 
The most notable event of this cruise was the discovery of the greatest ocean-depth 
as yet ascertained by soundings taken with the utmost care, and the results of which can 
be considered trustworthy. On the 23rd of March we stopped in lat. 11 24 N., long. 
143 0 16' E., and about midway in the narrow sea which separates Guam Island, the most 
southern of the Mariana group, from Uluthi, one of the western Caroline Islands. The depth 
was found to be 4575 fathoms, or about 5/4 English mdes. A second sounding, with a 
weight of 4 cwt. attached to the sounding-line (we had only used 3 cwt. in the previous 
sounding, not expecting so great a depth), gave 445 ° fathoms, or 26,700 feet. The rod of 
the sounding-machine contained a quantity of fine red mud or clay. The bottom-temperature, 
corrected for depth, was i° C., and three out of the four thermometers sent down in the two 
soundings returned to the surface crushed to atoms by the enormous pressure to which they 
had been exposed, the glass of the tubes being reduced to a fine white powder. These 
soundings show that the depths of the ocean, as yet ascertained, do not exceed the height of 
the loftiest mountains, that of Mount Everest, in the Himalayas, having been estimated at 
29,000 feet, while still higher summits have been reported in the same region. It is necessary 
