172 PROF. W. J. DAKIN : EXPEDITION TO THE 



runs roughly N.N.E.-S.S.W.) the reel: runs S.W. for a little distance, and 

 then curves round to continue in a north-westerly direction as the western 

 part of the encircling reef. Thus, there is no entrance into the lagoon over 

 the encircling reef between the northern extremity of Pelsart Island on the 

 east, and the northern end of the Western Reef (see text-fig. 8). On the 

 North, however, the lagoon is open to the channel between the Pelsart 

 and Easter Groups (the Zeewyk Channel), and (he encircling reef is 

 represented by a large number of scattered reefs and islands. There is 

 quite a collection of these at the north-eastern corner of the lagoon (the 

 Mangrove Islands of the Chart). On our second expedition we anchored 

 the lugger amidst these islets and used the motor dinghy for work in the 

 lagoon. On the first expedition we sailed the lugger through the lagoon 

 (beating all the way against the dominant southerly wind) to the southern 

 extremity of Pelsart Island, where we anchored not far from the ruins of a 

 wooden jetty. When still some distance away from the encircling reef one 

 hears the continued thunder of the breaking waves, for the ocean swell 

 comes in unhindered till it meets this coral barrier. One can often see the 

 white breakers when several miles away owing to mirage effects. This 

 effect was noted by Kent, whose observations at the Abrolhos Islands were 

 confined chiefly to the Pelsart Islands, and a half-tone production of a 

 photograph showing these breakers is given in his work 'The Naturalist in 

 Australia ' (page 132). 



A steady wash of water is apparently the usual occurrence over the southern 

 and south-western part of the encircling reef into the lagoon, and consequently 

 a current of some strength is met with in the latter, the water running from 

 south to north. As a result, the lagoon water to the north is more free from 

 debris than that towards the southern part of the lagoon. This factor 

 determines to a large extent the position of lagoon coral growths. 



The lagoon is roughly 11 sea miles across where it is widest, and about 

 8 miles from north to south. One does not meet with the same depths 

 that are found in the Easter or Wallaby Groups, and over a very considerable 

 part of the area of the lagoon the depth varies round two, three or four 

 fathoms. This applies to the whole of the southern end where the depth is 

 only 6-8 feet, except for a channel which is indicated on the chart and runs 

 S.S.E. towards the southern end of Pelsart Island. In this channel depths 

 round 10 fathoms are recorded. There is a very considerable difference 

 indeed between the floor of the higoon in different parts. At the southern 

 end it is flat, with a floor of level coral covered with but little sand, except 

 in patches. Probably the current is too strong for deposition of debris 

 except in certain places. No live coral growths were observed here. The 

 bottom of the lagoon near Pelsart Island, and about opposite the middle of 

 its length, is somewhat similar but with a greater deposit of sand. To the 

 north-east of the lagoon (the part shaded on the map, text-fig. 8, between 



