grotesque shape, or in thin films follows planes of stratification. It also occupies vertical cracks and joints. Besides these, certain large cylindrical hoilow fossils, growing one over another to the height of some yards and apparently rising contemporaneously with the chalk deposit, are entirely formed of flint. All these flints, almost without exception, show, when microscopically examined, marks of organic structure referable generally to sponges and spongiform bodies. Some idea of their appearance under the microscope may be obtained by referring to the illustration in the annexed plate (fig. g). The explanation of chalk, whatever it may be, must include a reasonable account of these contents, but as they are in some places very abundant and in others almost absent, it is clear that their presence is not absolutely necessary. That they are due to organic agency there cannot be a doubt, but whether they represent the protoplasm or Bathybius of Prof. Huxley, always at hand, and which may be supposed to silicify rapidly under certain conditions, or whether they are simple results of a quantity of silica introduced from time to time from without by thermal springs accumulating round spongy bodies containing siliceous spicules (see Plate figs. h, i, k, l) there is at present no sufficient evidence to determine. Parts of the upper chalk, as we have seen, also contain fragments of bryozoa, radiated animals, crustaceans, mollusks of all kinds, fishes, and reptiles: they even contain fragments of wood and a few pebbles. All these are consistent with the composition of the rock as a submarine mud deposited in open and deep water, for the recent investigations may be said to have cleared up all doubt as to the possibility of life of all known kinds in water of more than 2,000 fathoms, and the few foreign substances are no doubt the result of accidental drift. The only requirements of life, apparently indispensable both in water and air, are the free access of light and of certain gases and sufficient heat, and a temperature twelve or fifteen degrees above the freezing point of water appears to be sufficient for the rapid growth and multiplication of the Foraminifera, while a lower temperature is actually richer in species though infinitely more barren in the number of individuals.

It is no doubt necessary before we admit that chalk is foraminiferous mud that we should know its composition, and this has not yet been determined on a large scale. The result of a very simple analysis would seem to show that in some cases at least the foraminiferous mud or oaze contains more than 90 per cent. of carbonate of lime. Other examples, recently submitted by Mr. Gwynn Jeffreys, make it appear that not much more than 50 per cent. of some samples is of this material. It is clear that a few isolated analyses are not sufficient in a question of this magnitude, and thus a certain amount of doubt

rests as to the material. This will no doubt be removed before long by the assistance of the chemists.

Assuming, as is certainly probable, that foraminiferous mud is generally a nearly pure calcareous substance mixed with a small proportion of silica and some trace of organic matter, there can hardly be a doubt that its colour, texture, general nature, and contents, do correspond singularly with those of white chalk, and render it not unlikely that all those parts of Europe and Asia where chalk is now found were, during the cretaceous period, at least 8,000 feet below the sea. As some of them form hills of considerable height, a rise of at least 10,000 feet in places is required for the appearance of the rocks in their present position. There is nothing in this assumption in any way opposed to what is already known regarding the elevation of the earth's surface, during the tertiary period in Europe, Asia, and Africa. On the contrary, a change of level to this extent is indicated by the great mountain chains, all of which are modern, and all of which have probably been higher rather than lower than they now are during the tertiary period.

The necessity of a warm sea bottom during the accumulation of foraminiferous mud, and the fact that warm sea bottoms are quite independent of latitude and have nothing whatever to do with the climate of adjacent land, are perhaps among the most important of the recent investigations. The influence of depth on the nature and homogeneity of deposits is also remarkable. That animal life exists in all its activity and without any check in the deepest recesses of the ocean has now become more than probable, and that geologists must look to bathymetrical conditions and conditions of bottom temperature far more than they have hitherto done in considering the circumstances under which deposits have been made is perfectly clear.

As limestone of all kinds is apparently due to a large and rapid growth of animal organisms, while arenaceous deposits are chiefly abundant where life, if present, exists under less favourable conditions, and as heat appears to play an important part in rendering the sea bottom favourable or otherwise for rapid accumulations of calcareous matter, it becomes evident that the direction of marine currents is even more than has yet been recognised a prime agent in all geological causation. The diversion of the warm currents from their present course towards the north-east between Iceland and the Hebrides would at once check or cause to cease the accumulation of foraminiferous mud throughout the temperate latitudes of the north Atlantic. The depression of central Europe to become the bottom of a deep sea with an outlet into the Pacific would convey the warm currents eastwards, and produce accumulations which might rival the chalk in magnitude. On the other hand,

the existence of a barrier of land west of Ireland, extending southwards from Iceland, would cut off the warm current from the Gulf of Mexico and produce a boreal fauna in the sea, just as a considerable extension of land within the arctic circle would chill the climate of all northern European land, and bring down an icy cap to the Alps and Pyrenees.

We have only to look at the soundings already made, and compare the facts determined as to the depth of the Atlantic, to see how easily a comparatively small change in the relative level of the sea bottom must, by influencing the bottom temperature, modify and entirely alter the nature of the deposits. For this purpose a glance at the annexed chart (see Plate) will be sufficient. It will there be seen that undulations along the central line of the Atlantic canal, must divert currents which now convey warm water into latitudes very near the Arctic circle, while corresponding undulations across the ocean would affect such currents very little. On the other hand, it is well known that the great land undulations in our hemisphere have been rather in a direction parallel to the equator than from north to south, so that as there is a volcanic axis from Iceland southwards towards the African coast, indicated sometimes by actual eruption and very frequently by earthquakes, the movements are on the whole at right-angles, tending to separate still further the eastern from the western hemisphere, as the northern part of the old world is already separated from the southern.

Whatever may be the value of speculations of this kind, there can be no doubt of the necessity of further active explorations of the sea bottom, accompanied by observations of bottom and intermediate temperature in all seas. Hitherto the north Atlantic canal has alone been examined with any approach to system, and even there but a very small area has been looked at. The parts of this ocean to the south of the telegraph platform should be followed and soundings taken, with a view to discover the direction of the banks between which the warm stream runs towards the Arctic Ocean. Systematic search to connect, if possible, Iceland and the volcanic islands of the Atlantic off the coast of Africa, and thus to discover whether the fauna east and west of this line are identical, is greatly needed. A similar search northwards, following the warm channel in that direction, could not fail to yield important information, while the pursuit of the cold current bringing icebergs to its southern extremity after crossing the Gulf Stream might yield results little anticipated. The whole subject is one full of interest and promising a long continuance of important discovery. There is ample field for all, and it is hardly possible to imagine a more noble use of the resources in the possession of some of our wealthy owners of steam yachts, than a systematic

pursuit of dredging operations in the little visited parts of the ocean. Who can tell what treasures may reward those who first dredge in the Sargasso sea, or in the tropical waters of the Caribbean Sea and the Gulf of Mexico and in the Atlantic between Africa and America? That each cast of the dredge would bring up treasures of some kind is certain, provided only that there be a competent naturalist at hand to direct the work and record the results. Governments may and will vie with each other in this work. Whether the singular disinclination of our own Government and of naval commanders to employ ships for natural history work may be partly overcome, as might be supposed, by the recent success of the application of the Royal Society Council remains to be seen, but the American and Danish Governments have already intimated their intention of doing their share. The French are not likely to be far behind. There is ample room for all, and no fear need exist of any clashing of interests. More important facts than those resulting from widely-extended sounding and dredging operations can hardly be obtained, and at present the work done is as nothing compared with that which remains. There should be no jealousy in such a matter either among individuals or nations.

EXPLANATION OF PLATE LV.

Chart of the north Atlantic canal, showing several lines of soundings, marked in hundreds of fathoms, and the set of various stream and drift

currents.

a. Recent Globigerina from the Atlantic sea bottom (Wallich).

b, c. Varieties of form of Globigerina from shallow water.

d, e, f. Globigerinæ from the chalk.

g. Structure of flint highly magnified, showing sponge spicules.

h, i, k, l. Varieties of form of recent sponge spicules.

WHAT IS WINE?

BY A. DUPRÉ, Ph.D.,

LECTURER ON CHEMISTRY, WESTMINSTER HOSPITAL.

IN

N a former communication we have seen how, in the course of fermentation and subsequent maturing, the comparatively speaking simply constituted must is changed into the highly complex mixture wine. We will now consider somewhat more fully the quantitative relation of some of its most important constituents. Before doing so, however, it may be well once more to recall to mind the various substances hitherto detected in wine, and to contrast them, in a tabular form, with those found in the must.