120 PERCY SLADEN TRUST EXPEDITION. 
estate, the canes are known by the number of their varieties in chronological order. 
Thus one field may be planted with no. 287 and the next with 405. The methods of 
crossing and of the production of pure varieties from individuals designed to be self- 
fertilized in the next generation appeared to us, from the account we were given, to 
be eminently scientific. 
It would be a matter of great difficulty to estimate the age of Mauritius from topo. 
graphical considerations. During the hot season, from December to April, the island is 
subject to hurricanes, which, besides their wind-effects, often cause great floods. The 
effect which these produce is difficult to estimate, but they cause heavy falls of rock 
along the river-valley. The average rainfall varies from 40 inches on the northern coast 
to probably 150 inches on the hills. The greater part falls in the hurricane season, 
then the prevailing south-easterly trades often give place to west, or even north-west, 
winds. ‘The appearance of the deep river-gorges in the hard basalt is only compatible 
with considerable age, but the general fringing character of the reefs is opposed to this 
idea. Grand Port, it is true, is certainly formed by a barrier-reef, which has a deep 
lagoon between itself and the land, but it is not certain how far the attainment of this 
condition may have been aided by the elevation which we have traced there. On the 
whole, we are inclined to think that elevation has exercised a more material effect than 
at first seems probable. Although we found no indisputable evidence of its occurrence 
in any other district of the island, many points in the appearance of the coast suggest 
that the upheaval affected the whole of Mauritius. As far as we investigated them, the 
coral-recfs of the island are not to be compared with those of the Chagos or Maldives 
either in extent or in the richness of their fauna and flora, which we had the opportunity 
of examining in greater detail in the Museum at Port Louis. Indeed, Mauritius, the 
sea-water of which has an average temperature of about 72°, is not far off the southern 
limit of coral-builders, so that too much stress must not be laid on the paucity of its 
reefs. There is a depth of 2160 fathoms between Bourbon and Mauritius and of 2200 
jathoms between the latter and Rodriguez. Probably all the three Mascarenes were 
separate formations, and have been subject to independent local elevations and 
depressions. Of them, Mauritius perhaps is the oldest, and would certainly seem to be the 
most stable. That there was any direct land-connection at any time between the three 
seems to be doubtful, though probably all three obtained their life from the same source. 
On Monday, Aug. 21, we left Port Louis for the second part of our cruise, and 
anchored that night in the outer roadstcad close to the lightship. Before we left, our 
dredging-wire arrived by the mail-steamer, but only just in time. On the Tuesday we 
steamed down to the south-west point of the island to inspect the coast. As this was 
the most southern point we should visit, we took a series of plankton hauls about 5 miles 
west of the mouth of Black River. At first we used serial nets at every 25 fathoms 
down to 150 fathoms, and then continued the same by a second series to 300 fathoms. 
We also tried our large net of 8 meshes to the inch, letting out 240 fathoms of wire. The 
wire, however, soon began to jerk and the net to approach the surface. Evidently we 
had caught a shark, or sone other large fish, as such remains of the net as we secured 
were torn to rags. In the evening we anchored close inshore in Black River Bay, and 
