22 PERCY SLADEN TRUST EXPEDITION. 
during these nights the sea never showed even a spark of phosphorescence, because in 
similar weather in the south-west monsoon off Minikoi, in June and July of 1899, 
Gardiner and Borradaile had frequently noticed a particular brillianey, evidently 
produced by a large variety of forms. The time, however, was more than a month later, 
and, of course, by then there would have been a very considerable drift of the sea from 
west to east. It might, too, have been a breeding-time for the pelagic organisms, as it 
certainly was for the reef-living forms. 
During this time we busied ourselves in getting our gear into order and opening cases 
ready for work. Corp. Cronk, in charge of the small detachment of Royal Marines on 
board, who had been told off to assist us, was instructed in keeping the meteorological 
log, in which he became extraordinarily proficient. We also for a week continuously 
checked the four quartermasters in reading the various instruments. These consisted 
of barometer with thermometer attached, wet- and dry-bulb thermometers, and thermo- 
meter for sea-water temperature, which were all regularly read six times a day, just 
before the watches were changed. At the same times or at noon particulars of the 
course, distance by log, direction and force of winds, clouds, weather, and state of the 
sea-surface (waves and swell), the position of the ship, and currents experienced in 
the previous 24 hours as well as the compass-error were entered. Similar logs are kept 
by most large passenger-liners, and are forwarded, when convenient, to the Meteorological 
Office, from which it is enabled to draw up and correct its charts. 
We put down our first sounding on the early morning of May 14, obtaining 
2121 fathoms. Unfortunately the wire parted, and, as we did not know our position, 
we lay-to until the evening, when we managed to get sights. We then sounded again, 
2135 fathoms, about 80 miles to the east-south-east of Addu Atoll, finding a hard bottom. 
Doubt is always cast on the statement that the bottom is hard when deep soundings are 
concerned, as it rests generally on negative evidence, no sample having been obtained 
with the lead. However, in this case there was no evidence that the valves failed to 
act, and likewise in three soundings further east of 1600, 1596, and 2100 fathoms no 
bottom-sample was obtained. If the bottom is really hard, it can only be explained by 
the existence of a deep current sweeping round the south of the Maldives, diverted 
partially no doubt by the ridge on which they are situated. 
Thence we ran down to lat. 2° 45’ 8., where we ran a series of soundings across the 
direct line between the Maldive and Chagos Archipelagoes, obtaining depths of 2129, 
2078, 2008, 2062, and 2082 fathoms. These showed us that the ridge on which the 
Maldives are situated, which in its southern part lies at a depth of about 1000 fathoms, 
tails off to the south of Addu in about 75 miles to roughly 2000 fathoms, at which 
depth it continues until the Chagos Bank commences to rise. The distance from Addu 
to the north end of the Chagos (¢. e. Speakers Bank) is 240 miles, and the approximate 
depth is not more than 2300 fathoms on either side of what is evidently a low ridge 
connecting the two groups. These are the first soundings which have been put down 
across the line between the two groups, the ‘ Valdivia’ Expedition having unaccountably 
omitted this important work. If the Maldive and Chagos atolls are taken to indicate 
the sites of lands which have disappeared owing to subsidence, some more definite 
