the North Sea. It has been generally agreed that the enormous increase of fishing power during the last forty years or so has reduced the number of large plaice, so that the average size of that fish caught in our home waters has become smaller, although the total number of plaice landed had continued to increase up to the year of the outbreak of war. Since then, from 1914 to 1919, there has of necessity been what may be described as the most gigantic experiment ever seen in the closing of extensive fishing grounds. It is still too early to say with any certainty exactly what the results of that experiment have been, although some indications of an increase of the fish population in certain areas have been recorded. For example, the Danes, A. C. Johansen and Kirstine Smith, find that large plaice landed in Denmark are now more abundant, and they attribute this to a reversal of the pre-war tendency, due to less intensive fishing. But Dr. James Johnstone has pointed out that there is some evidence of a natural periodicity in abundance of such fish and that the results noticed may represent phases in a cyclic change. If the periodicity noted in Liverpool Bay (see Johnstone, Report Lancs. SeaFish. Lab. for 1917, p. 60; and Daniel, Report for 1919, p. 51) holds good for other grounds it will be necessary in any comparison of pre-war and post-war statistics to take this natural variation in abundance into very careful consideration.

In the application of oceanographic investigations to sea-fisheries problems, one ultimate aim, whether frankly admitted or not, must be to obtain some kind of a rough approximation to a census or valuation of the sea-of the fishes that form the food of man, of the lower animals of the sea-bottom on which many of the fishes feed, and of the planktonic contents of the upper waters which form the ultimate organised food of the sea-and many attempts have been made in different ways to attain the desired end.

Our knowledge of the number of animals living in different regions of the sea is for the most part relative only. We know that one haul of the dredge is larger than another, or that one locality seems richer than another, but we have very little information as to the actual numbers of any kind of animal per square foot or per acre in the sea. Hensen, as we have seen, attempted to estimate the number of food-fishes in the North Sea from the number of their eggs caught in a comparatively small series of hauls of the tow-net, but the data were probably quite insufficient and the conclusions may be erroneous. It is an interesting speculation to which we cannot attach any economic importance. Heincke says of it: "This method appears theoretically feasible, but presents in practice so many serious difficulties that no positive results of real value have as yet been obtained."

All biologists must agree that to determine even approximately the number of individuals of any particular species living in a known area is a contribution to knowledge which may be of great economic value in the case of the edible fishes, but it may be doubted whether Hensen's methods, even with greatly increased data, will ever give us the required information. Petersen's method, of setting free marked plaice and then assuming that the proportion of these recaught is to the total number marked as the fishermen's catch in the same dis

trict is to the total population, will only hold good in circumscribed areas where there is practically no migration and where the fish are fairly evenly distributed. This method gives us what has been called "the fishing coefficient," and this has been estimated for the North Sea to have a probable value of about 0.33 for those sizes of fish which are caught by the trawl. Heincke (F. Heincke, Cons. Per. Internat. Explor. de la Mer, "Investigations on the Plaice," Copenhagen, 1913), from an actual examination of samples of the stock on the ground obtained by experimental trawling (the catch coefficient"), supplemented by the market returns of the various countries, estimates the adult plaice at about 1,500 millions, of which about 500 millions are caught or destroyed by the fishermen annually.

It is difficult to imagine any further method which will enable us to estimate any such case as, say, the number of plaice in the North Sea where the individuals are so far beyond our direct observation and are liable to change their positions at any moment. But a beginning can be made on more accessible ground with more sedentary animals, and Dr. C. G. Joh. Petersen, of the Danish Biological Station, has for some years been pursuing the subject in a series of interesting Reports on the "Evaluation of the Sea" (see Reports of the Danish Biological Station, and especially the Report for 1918 "The Sea Bottom and its Production of Fish Food"). He uses a bottomsampler, or grab, which can be lowered down open and then closed on the bottom so as to bring up a sample square foot or square metre (or in deep water one-tenth of a square metre) of the sand or mud and its inhabitants. With this apparatus, modified in size and weight for different depths and bottoms, Petersen and his fellow-workers have made a very thorough examination of the Danish waters, and especially of the Kattegat and the Limfjord, have described a series of “animal communities" characteristic of different zones and regions of shallow water, and have arrived at certain numerical results as to the quantity of animals in the Kattegat expressed in tons-such as 5000 tons of plaice requiring as food 50,000 tons of "useful animals" (mollusca and polychaet worms), and 25,000 tons of starfish using up 200,000 tons of useful animals which might otherwise serve as food for fishes, and the dependence of all these animals directly or indirectly upon the great Beds of Zostera, which makes up 24,000,000 tons in Kattegat. Such estimates are obviously of great biological interest, and even if only rough approximations, are a valuable contribution to our understanding of the metabolism of the sea and of the possibility of increasing the yield of local fisheries.

But on studying these Danish results in the light of what we know of our own marine fauna, although none of our seas have been examined in the same detail by the bottom-sampler method, it seems probable that the animal communities as defined by Petersen are not exactly applicable on our coasts and that the estimates of relative and absolute abundance may be very different in different seas under different conditions. The work will have to be done in each great area, such as the North Sea, the English Channel, and the Irish Sea, independently. This is a necessary investigation, both biological and physical, which

lies before the oceanographers of the future, upon the results of which the future preservation and further cultivation of our national sea-fisheries may depend.

It has been shown by Johnstone and others that the common edible animals of the shore may exist in such abundance that an area of the sea may be more productive of food for man than a similar area of pasture or crops on land. A Lancashire mussel bed has been shown to have as many as 16,000 young mussels per square foot, and it is estimated that in the shallow waters of Liverpool Bay there are from 20 to 200 animals of sizes varying from an amphipod to a plaice on each square metre of the bottom (Conditions of Life in the Sea, Cambridge Univ. Press, 1908).

From these and similar data which can be readily obtained, it is not difficult to calculate totals by estimating the number of square yards in areas of similar character between tide-marks or in shallow water. And from weighings of samples some approximation to the number of tons of available food may be computed. But one must not go too far. Let all the figures be based upon actual observation. Imagination is necessary in science, but in calculating a population of even a very limited area it is best to believe only what one can see and measure.

Countings and weighings, however, do not give us all the information we need. It is something to know approximately the number of millions of animals on a mile of shore and the number of millions of tons of possible food in a sea-area, but that is not sufficient. All food-fishes are not equally nourishing to man, and all plankton and bottom invertebrata are not equally nourishing to a fish. At this point the biologist requires the assistance of the physiologist and the bio-chemist. We want to know next the value of our food matters in proteids, carbohydrates, and fats, and the resulting calories. Dr. Johnstone, of the Oceanography Department of the University of Liverpool, has already shown us how markedly a fat summer herring differs in essential constitution from the ordinary white fish, such as the cod, which is almost destitute of fat.

Professor Brandt, at Kiel, Professor Benjamin Moore, at Port Erin, and others have similarly shown that plankton gatherings may vary greatly in their nutrient value according as they are composed mainly of Diatoms, of Dinoflagellates, or of Copepoda. And, no doubt, the animals of the "benthos," the common invertbrates of our shores, will show similar differences in analysis.* It is obvious that some contain more solid flesh, others more water in their tissues, others more calcareous matter in the exoskeleton, and that therefore weight for weight we may be sure that some are more nutritious than the others; and this is probably at least one cause of that preference we see in some of our bottom-feeding fish for certain kinds of food, such as polychaet worms, in which there is relatively little waste, and thinshelled lamellibranch molluscs, such as young mussels, which have a highly nutrient body in a comparatively thin and brittle shell.

*Moore and others have made analyses of the protein, fat, etc., in the soft parts of Sponge, Ascidian, Aplysia, Fusus, Echinus, and Cancer at Port Erin, and find considerable differences-the protein anging, for example, from 8 to 51 per cent, and the fat from 2 to 14 er cent (see Bio-Chemical Journ. vi. p. 291).

My object in referring to these still incomplete investigations is to direct attention to what seems a natural and useful extension of faunistic work, for the purpose of obtaining some approximation to a quantitative estimate of the more important animals of our shores and shallow water and their relative values as either the immediate or the ultimate food of marketable fishes.

Each such fish has its "food-chain" or series of alternative chains, leading back from the food of man to the invertebrates upon which it preys and then to the food of these, and so down to the smallest and simplest organisms in the sea, and each such chain must have all its links fully worked out as to seasonal and quantitative occurrence back to the Diatoms and Flagellates which depend upon physical conditions and take us beyond the range of biology-but not beyond that of oceanography. The Diatoms and the Flagellates are probably more important than the more obvious sea-weeds not only as food, but also in supplying to the water the oxygen necessary for the respiration of living protoplasm. Our object must be to estimate the rate of production and rate of destruction of all organic substances in the sea.

To attain to an approximate census and valuation of the sea-remote though it may seem-is a great aim, but it is not sufficient. We want not only to observe and to count natural objects, but also to understand them. We require to know not merely what an organism is-in the fullest detail of structure and development and affinities --and also where it occurs-again in full detailand in what abundance under different circumstances, but also how it lives and what all its relations are to both its physical and its biological environment, and that is where the physiologist and especially the bio-chemist, can help us. In the best interests of biological progress the day of the naturalist who merely collects, the day of the anatomist and histologist who merely describe, is over, and the future is with the observer and the experimenter animated by a divine curiosity to enter into the life of the organism and understand how it lives and moves and has its being. "Happy indeed is he who has been able to discover the causes of things."

Cardiff is a sea-port, and a great sea-port, and the Bristol Channel is a notable sea-fisheries centre of growing importance. The explorers and merchant venturers of the South-West of England are celebrated in history. What are you doing now in Cardiff to advance our knowledge of the ocean? You have here an important university centre and a great modern national museum, and either or both of these homes of research might do well to establish an oceanographical department, which would be an added glory to your city and of practical utility to the country. This is the obvious centre in Wales for a sea-fisheries institute for both research and education. Many important local movements have arisen from British Association meetings, and if such a notable scientific development were to result from the Cardiff meeting of 1920, all who value the advance of knowledge and the application of knowledge to industry would applaud your enlightened action.

But in a wider sense, it is not to the people of Cardiff alone that I appeal, but to the whole population of these Islands, a maritime people

who owe everything to the sea. I urge them to become better informed in regard to our national sea-fisheries and take a more enlightened interest in the basal principles that underlie rational regulation and exploitation of these important industries. National efficiency depends to a very great extent upon the degree in which scientific results and methods are appreciated by the people and scientific investigation is promoted by the Government and other administrative authorities. The principles and discoveries of science apply to aquiculture no less than to agriculture. increase the harvest of the sea the fisheries must be continuously investigated, and such cultivation as is possible must be applied, and all this is clearly a natural application of the biological and hydrographical work now united under the science of Oceanography.

CORRESPONDENCE.

ELECTRONS AND NUCLEI.

Το

To the Editor of the Chemical News. SIR,--The idea that the electrons revolve round the positive nuclei as central suns, according to the Bohr-Rutherford atom theory, is supported by much evidence; but when one considers an assemblage of nuclei as in either an atom structure or a crystal structure, more or less complex, certain difficulties seem to present themselves.

Without going into all the "pros and cons," it seems worth while considering the electrons arranged in pairs, as in the accompanying diagram (taken as a plan view), and revolving as shown when certain conditions are impressed upon the assemblage. Just what these conditions would be it is difficult to say, but there appears to be no reason why this arrangement should not be a stable one when all the electro-dynamic consequences, as involved in a three-dimensional structure, are worked out.

A sectional elevation view would show the linking up of the nuclei by lines of force (bonds) emanating from each negative electron. Each pair of electrons would be common to two nuclei situated at opposite ends of the axis of rotation. Each axis might represent a line of magnetic force so that if all the electron pairs were revolving in the same direction the axial lines would be extended and a magnetic state would be represented. In the diagram the large black dots represent the positive nuclei.-I am, &c.,

NOTES.

F. H. LORING.

INSTITUTE OF METALS. Autumn Meeting, Barrow-in-Furness, September 15 and 16, 1920.The following is a list of the Papers that are expected to be submitted :

W. E. Alkins, M.Sc. (Manchester), on "The Immiscibility of Metals from the Point of View of the Phase Rule."

Engineer Lieutenant-Commander G. B. Allen, R. N. (London), on "Service Experience with Condensers."

T.

G. Bamford, M.Sc. (Birmingham), and W
Ballard (Birmingham), on "The Influence of
Gases on High-Grade Brass."

Kathleen E. Bingham, B.Sc. (Teddington), on "The Allotropy of Zinc."

Professor H. C. H. Carpenter, M.A., Ph.D., A.R.S.M., F.R.S. (London), and Constance F. Elam (New Barnet), on "Crystal Growth and Recrystallisation in Metals."

J. H. S. Dickenson (Sheffield), "Note on a Failure of Manganese Bronze."

D. Hanson, M.Sc. (Teddington), and Marie L. V. Gayler, B.Sc. (Teddington), on "The Constitution of the Alloys of Aluminium and Magnesium."

O. F. Hudson, D.Sc. (London), and J. H. Darley (London), on "The Constitution and Structure of Certain Tin-Antimony-Copper Alloys." F. Johnson, M.Sc. (Birmingham), on "Some Features in the Behaviour of Beta Brass when Cold-Rolled."

R.

T. Rolfe, F.I.C. (Bedford), on "The Effect of
Increasing Proportions of Antimony and of
Arsenic respectively upon the Properties of
Admiralty Gun-Metal."

H. B. Weeks, F.I.C., "Notes on Brass Foundry Practice at Messrs. Vickers Limited, Barrowin-Furness."

Members intending to take part in the discussion of any of the Papers can be supplied with a copy a week before the Meeting on application to the Secretary. Copies of all Papers will, it is hoped, be available at the Meeting for the use of Members who have not previously received copies, and those who are unable to attend will be subsequently be supplied, on application, with a copy of any Paper of which prints remain. In the Discussion following the reading of the Papers each speaker will be limited to ten minutes, unless the time should be extended by the Chairman. Speakers who are unable to give more than a summary of their views in the time available may send a written statement to the Secretary for publication in the December issue of the Journal, such statement to be in the hands of the Secretary not later than noon on October 16, 1920.

The

INSTITUTION OF MINING ENGINEERS. Thirty-first Annual General Meeting of the Members of the Institution of Mining Engineers will Manchester, on Wednesday, September 15, 1920, be held in the Lord Mayor's Parlour, Town Hall, at 10.30 a.m. Arrangements have been made for visits to places of interest and works on September 16 and 17. In order that the necessary arrangements may be made, members are desired to make application for tickets for the Manchester Meeting, not later than September 7, to Mr. N. T. Williams, Hon. Secretary of the Manchester Geological and Mining Society, 5, John Dalton Street, Manchester. All applications for the Dinner, Excursions, etc., received after that date will be subject to the accommodation proving sufficient. Attention of members is drawn to the desirability of increased membership, and they are urged by the President to propose suitable persons for any of the classes of membership.

ELECTRICITY METERS FOR NEW ZEALAND.—In a recent communication H.M. Trade Commissioner in New Zealand (Mr. R. Dalton) gives some particulars obtained from the Chief Electrical Engineer, Public Works Department, Wellington, on the types of meter found suitable for that market. It is stated that the maximum demand system is very suitable for hydro-electric power systems, and would have been used more widely if a cheaper and more accurate instrument were available. So far the only reasonably cheap types are wanting in accuracy. The clockwork types are too expensive. A good serviceable maximum demand indicator, costing, say, £2 to £4 without wattmeter, or £3 to £6 with wattmeter dial as well as maximum demand dial, would find a ready sale. A satisfactory commercial maximum K.V.A. meter suitable for service on demands of 5 up to 500 K.V.A. graduated for 400 volts, 3300 volts and 11,000 volts is required. So far no suitable instrument for measuring maximum K.V.A. has been available, and consequently it is necessary to take the maximum kilowatts averaged over half-an-hour and deduce there from the maximum K.V.A. from the power factor observed during heavy loads. This system is obviously unsatisfactory if a suitable maximum K.V.A. or maximum current measuring instrument is available. The standard frequency for New Zealand is 50 cycles. A copy of the latest scale of charges has been forwarded and may be seen by British firms on application to the Enquiry Room at the Department, at 35, Old Queen Street, quoting D.O.T./2218/ED. According to this four rates are in operation, viz., Rate A, a fixed rate for domestic and farm service; Rate B, a two-rate system for domestic purposes; Rate C, meter rate for general purposes; and Rate D, maximum demand for general purposes. Of the wholesale rates the most popular is Rate D based on maximum K.V.A. demand, and a large number of consumers will come on to this rate in the Canterbury and Waikato districts. The Chief Electrical Engineers will be glad to hear from firms offering purely British material likely to be of use for the above purposes.

ALSATIAN POTASH.-The French Minister of Agriculture, in a notice published in the Journée Industrielle reminds persons interested in the purchase of Alsatian potash salts that trade in this commodity is now free. He adds that orders for potash are no concern of his department, and that they should be sent either to Mulhouse, or to the various representatives to the "Société Commerciale des potasses d'Alsace." Whereas before the war the consumption of pure potash in France did not exceed 37,000 tons a year, the mines of Alsace were able to send to France no less than 47,000 tons of pure potash in the year 1919, and 30,000 tons in the first half of the present year. Many orders which were given some time ago have not yet been delivered, but the Minister of Agriculture has been able to arrange that a sufficient number of trains shall be placed at the disposal of the mines, to ensure the delivery of 5000 to 8000 tons of pure potash a month. It is therefore to be presumed that delays in delivery will no longer occur.

A WORLD'S MARKET IN PARIS.-The Federation of British Industries has undertaken the direct representation for Great Britain and

the

Dominions of the Paris "Marche du Monde." The idea of establishing a "World's Market" in Paris was conceived in 1919, and from the first received the close attention and approval of the Federation. After a year's work the scheme has now come very close to practical realisation. The site for the building is being cleared, and contracts for its erection have been placed. Already a very considerable number of American, French, Italian, and other Continental, as well as some British firms have reserved space in the "Marche du Monde" when completed. At this stage the Federation of British Industries has decided in the interests of the British manufacturer to give active support to the scheme. It is most important that the Industry of this country should be fully represented at this great gathering place of trade. It is with the object of assuring that an adequate share of space should be allotted to British firms in the "Marche du Monde" and that their interests should be properly protected that the F.B.I. has decided to take over its representation here and in the Dominions overseas. The Federation recommends manufacturers engaged in or contemplating export trade to give the following brief outline of the "Marche du Monde" their earnest consideration. Briefly, the idea of the promoters is to systematise and centralise international commerce by erecting in Paris-which geographically and historically is the focus of Europe-a great commercial centre, in which the manufactures of all nations can be permanently exhibited under one roof and therefore readily accessible to buyers from all countries visiting Paris. In effect, it is a development of the City Trade Fair for which France is famous. But whereas the City Fair is temporary and local, the "Marche du Monde" will be permanent and international. Both buyer and seller will benefit, and it is for this reason that the appeal made by the "Marche du Monde" to both buyer and seller will be readily appreciated. It will enable the prospective buyer to find the firms and goods he wishes to see congregated under one roof; to make his choice from the products of many countries, with a fraction of the time, energy, and expense entailed in visiting isolated firms scattered through a multitude of towns in a dozen different countries. Conversely, it will enable the manufacturer not only to reach many more buyers, but to get into direct touch with them, and at the same time to cut expenses by obviating the necessity for so many agents or so much advertisement. It will be possible for a foreign firm to maintain a Paris or Continental Branch at a mere fraction of the cost which would otherwise have to be incurred. An Office in the building may be taken for as little-taking a favourable exchange into consideration-as £100 per year. Although it is difficult to say what the total expenditure will be, an opinion is expressed that the expenses of an office in the "Marche du Monde" looked after by a whole-time clerk who would be under the supervision of the firm's agent, will not cost more than £300 a year. It is hoped that these facts will induce manufacturers in this country to consider the matter very carefully. Any further information desired may be obtained immediately on application to the "Marche du Monde," Exhibition Section of the Federation of British Industries, 39, St. James's Street, London,