Det. 22, 1885] 
NATGRE 
613 
bottom. Where the depth is not very great only the thinnest 
and most delicate shells are removed, and the others accumulate, 
forming vast deposits; with increasing depth other shells dis- 
appear, only the thicker ones reaching the bottom ; but in the 
very greatest depth nearly every trace of these surface shells is 
removed, or we find them making up but 1 or 2 per cent. of the 
deposit. It is possible that this process of solution of the shells 
may be somewhat accelerated in the deepest layers of water by 
the great pressure. 
In the deepest parts of the abysmal areas, where the car- 
bonate of lime shells are either wholly or partially removed from 
the bottom, there are met with those peculiar deep-sea clays, the 
origin of which has been the subject of considerable discussion. 
The: are principally made up of clayey matter resulting from 
the «...ntegration of volcanic rocks, and derived chiefly from 
floatiu_s pumice and showers of volcanic ashes. Mixed up with 
these clayey and volcanic materials are thousands of sharks’ 
teeth, some of them of gigantic size, and evidently belonging to 
extinct species, also very many ear-bones, and a few of the 
other bones of whales, some of them also probably belonging to 
extinct species. These organic fragments are generally much 
decomposed and surrounded and infiltrated by depositions of 
peroxide of manganese, which is a secondary product arising 
from the decomposition of the volcanic material in the deposits. 
Again, we have in some places numerous zeolitic minerals and 
crystals formed in the clay, also as secondary products. Lastly, 
there are numerous minute spherules of native iron and other 
rare substances, covered with a black coating of oxide, which 
are referred with great certainty to a cosmic origin—probably 
the dust derived from meteoric stones as they pass through the 
higher regions of our atmosphere. Quartz, which is so 
abundant as a clastic element in deposits around the continents, 
is almost absent from the deposits of the abysmal regions. 
In the abysmal regions, then, which cover one half of the 
earth’s surface, which are undulating plains from two to five 
miles beneath the surface of the sea, we have a very uniform set 
of conditions: the temperature is near the freezing point of 
fresh water, and the range of temperature does not exceed 7°, 
and is constant all the year round in any one locality ; sunlight 
and plant-life are absent, and although animals belonging to all 
the great types are present, there is no great variety of form nor 
abundance of individuals ; change of any kind is exceedingly 
slow. In the more elevated portions of the regions the deposits 
consist principally of the dead shells and skeletons of surface 
animals, in the more depressed ones they consist of a red clay 
mixed with volcanic fragmental matter, the remains of pelagic 
vertebrates, cosmic dust, and manganese iron nodules and 
zeolitic crystals, the latter being secondary products arising 
from the decomposition of the minerals which have long re- 
mained exposed to the hydrochemical action of sea-water. The 
rate of accumulation is so slow in some of these clays that we 
find the remains of tertiary species lying on the bottom alongside 
the remains of those inhabiting the present seas. It has not yet 
been possible to recognise the analogues of any of the deposits 
now forming in the abysmal regions in the rocks making up the 
continents. 
It is quite otherwise in the areas bordering the continents— 
the uncoloured areas on the maps. Almost all the inatter 
brought down to the ocean in suspension is deposited in this 
region, which is that of variety and change with respect to light, 
temperature, motion, and biological relations. It extends from 
the sea-shore down, it may be, to a depth of three or four miles, 
and outwards horizontally from 60 to 300 miles, and includes 
all partially inclosed seas, such as the North Sea, Mediterranean, 
Caribbean, and many others. The upper or continental margin 
of the area is clearly defined by the coast line, which is continu- 
ally changing from breaker action, elevation, and subsidence ; 
the lower or abysmal margin of the region is less clearly marked 
out, passing insensibly into the abysmal regions and terminating 
where the mineral particles from the neighbouring continents 
disappear from the deposils. In the surface waters the temper- 
ature varies from over 80° in the equatorial to 28° in the Polar 
regions, and from the surface to the ice-cold water at the lower 
margins of the regions there is in the tropics an equally great 
range of temperature. Plants and animals flourish luxuriantly 
near the shore, and animals extend in relatively great abundance 
down to the lower limits of the region. Here we find now in 
process of formation deposits which will form rocks similar to 
those making up the great bulk of continental land, such as 
schists, shales, sandstones, marls, greensands, and chalks; the 
glauconitic grains of the green muds and phosphatic nodules 
can be traced in all stages of formation, and probably, though 
much less certainly, the initial stages in the formation of flint. 
Throughout all geological time the deposits formed in this 
border or transitional area appear to have been pushed, forced, 
and folded up into dry land, through the secular cooling of the 
earth and the necessity of the outer crust to accommodate itself 
to the shrinking solid nucleus within. These depositions do not in 
themselves cause elevation or subsidence, but most probably the 
changes of pressure, resulting from them, tend to destroy the 
existing equilibrium and to produce lines of weakness along the 
borders of the continents and in the regions of enclosed and par- 
tially enclosed seas, with the result that the borders of conti- 
nental land have been more frequently thrown into folds and 
have suffered greater lateral thrusts than any other regions on 
the surface of the earth. F 
On the other hand, while we know that there are vast deposits 
of carbonate of lime taking place over some portions of the 
abysmal regions, and that volcanic outbursts occur in others, 
still these are not comparable with the great changes which have 
taken place in the past, and are now taking place, on the con- 
tinents and along their borders. 
When the coral atolls and barrier reefs which are scattered 
over the tropical regions of the great oceans are examined in 
the light of recent discoveries, it is found that their peculiar 
form and structure can be accounted for by the truncation of 
some submarine cones through breaker action; by the upward 
growth of others through the accumulation of marine deposits ; 
by the solution of dead coral through the action of sea-water ; 
and lastly by a study of the source and direction from which the 
food supply reaches the reef-building animals. hat this in all 
probability is the true history of the origin of these marvellous 
structures is further confirmed by the recent examination of the 
upraised coral atolls of the Pacific by Dr. Guppy, and the re- 
searches of Mr. Buchanan itito the characters of oceanic banks 
and shoals. Coral atolls and barrier reefs, instead of pointing 
out great and general subsidences, must be regarded rather as 
indicating areas of great permanence and stability. 
The results of many lines of investigation, then, seem to show 
that in the abysmal regions we have the most permanent areas 
of the earth’s Surface, and he is a bold man who still argues that 
in Tertiary times there was a large area of continental land in 
the Pacific, that there was once a Lemuria in the Indian Ocean, 
or a continental Atlantis in the Atlantic. 
In this rapid review of recent oceanographical researches my 
chief object has been to show you the wide range of the observa- 
tions, for every science has been enriched by a large store of 
new facts. It matters little whether the opinions which I have 
given as to the bearing of some of these be correct or not ; for 
the observations are now or will soon be in the hands of scien- 
tific men, and errors in interpretation or deduction will soon 
be exposed. The great point is that there has been a vast 
addition to human knowledge, and it must be a matter of satis- 
faction that our own country has taken so large a share in these 
important investigations as to call forth the admiration of the 
scientific men of all countries. You have learnt from the 
President’s address that there is usually not much to say in com- 
mendation of the Government for its liberality to science. But 
in the matter of deep-sea investigation, neglecting mere details, 
we can say that the successive Governments of the Queen during 
the past twenty years have, either from design or by accident, 
undertaken a work in the highest interests of the race, have 
carried it on in no mean or narrow patriotic spirit, and are likely 
to carry it to a termination in a manner worthy of a great, free, 
and prosperous people. 
ON A SUPPOSED PERIODICITY OF THE 
CYCLONES OF THE INDIAN OCEAN SOUTH 
OF THE EQUATOR} 
]N papers printed in the Reforts for 1872, 1873, 1874, and 
1876, I endeavoured to show that there were grounds for 
supposing that the cyclones of the Indian Ocean south of the 
equator increased in number, extent, and intensity from a 
minimum in one year to a maximum in another, and then 
decreased to a minimum, the period or cycle apparently corre- 
sponding with the eleven-year period of solar activity. 
From the data given in the last of these papers (Aeport for 
® Paper by Mr. Charles Meldrum, F.R.S., read at the British Association. 
