Philosophical Society, Nov. 25-On the appearance of an extra digit on the hind limbs and then on both fore and hind limbs in two successive generations, and its bearing on the theory of Pangenesis, by Mr. N. Goodman. A cow had three welldeveloped toes on each hind limb, besides the two ordinary rudiments. Her calf (by a normal bull) had the same peculiarity. This has two calves (by normal bulls). The first, a cow, had the toes as in the other cases, but rather less developed; the second, a bull, had three toes on all four feet. The writer pointed out that this peculiarity might be explained by (1) atavism, (2) certain modifications of the proliferous function by external causes (3) correlation of growth, supplementing the former. He thought it could not be explained by atavism, nor by the second cause, but by the third, and discussed its bearing on his theory of Pangenesis.-A communication was received from Mr. W. H. Stanley on a Pneumatical design for saving life at sea. The process was by the expansion of condensed air stored in reservoirs.

LEEDS

Naturalists' Field Club and Scientific Association, Nov. 26.-Mr. J. W. Taylor on behalf of Mr. W. Nelson, of Birmingham, read a paper on "The Lymnæidæ of the Birmingham district," giving a catalogue of nineteen species found within five miles of Birmingham, against the twenty-three at present included in the British fauna. He also recorded twentyfour varieties for that district. The absence of the remaining four species was readily accounted for, on the ground either of their extreme rarity, or of their recent introduction into these islands. Planorbis dilatatus has recently been imported along with cotton; Lymnæa involuta has never been found away from its original locality, Killarney; while Planorbis lacustris and Lymnca glutinosa are excessively rare. The following is a list of the nineteen species found within five miles of Birmingham. Planorbis nitidus, P. nautileus, P. albus, P. glaber, P. spirorbis, P. vortex, P. carinatus, P. complanatus, P. corneus, Physa hypnorum, P. fontinalis, Lymnæa peregra, L. auricularia, L. stagnalis, L. palustris, L. truncatula, L. glabra, Ancylus fluviatilis, A. lacustris.

RIGA

Society of Naturalists, Jan. 24 (Feb. 5, N.s.)-M. C. Berg noticed the damage done to some peas by the larva of Endrosis lacteella.-M. Gögginger called attention to a yellow lucerne, identified by him with Medicago media, which he found near Hapsal, and recommended for cultivation, especially on account of its deep roots. Dr. Buhse doubted the identification of the plant, and stated that Medicago media is a hybrid of M. sativa and falcata, and that when cultivated it reverts to the type of the former species in a few years.-The aurora of February 4 was referred to by M. Schroeder and Prof. Schell. The former found no traces of polarisation, but in the spectroscope a broad greenish yellow line made its appearance. Prof. Schell's paper included notices of the phenomenon from various sources.

February 7 (19 N.S.) Dr. Nauck exhibited and described a maximum and minimum thermometer constructed on a new principle. It is a U-shaped tube, having one upright limb terminating in a bulb, and the other bent inwards and then downwards into a large cylindrical portion. The lower part of the U-tube is filled with mercury, and the rest with alcohol, except the bulb of the upright tube, the greater part of which is empty. The floats are of glass, enclosing an iron wire, and are fixed in the tubes by means of bent human hairs.-Dr. Buhse gave a detailed description of the parasitic fungi of infectious diseases, in which he referred to those affecting plants, animals, and man, and especially noticed the relation of Bacteria to

disease.

February 21 (March 4, N.S.)-M. Schroeder announced that two days previously (March 2, n.s.) he observed a distinct zodiacal-light about 8 o'clock P.M.-M. Frederking read a second part of his memoir on the History of Chemistry, in which he referred first to the discovery of oxygen by Priestley and Scheele, and then passed to the consideration of Lavoisier's labours.

February 28 (March 11, N.S.)—M. H. Westermann reported upon a work by Fechner entitled "Experimental Esthetics," in which the author endeavours to investigate experimentally the

general principles of symmetry. This report presents some curious and interesting points; the questions raised by it were discussed by several of the members present.

GOTTINGEN

Royal Society of Sciences, Aug. 3.-M. G. Meissner com municated a paper by Dr. Hartwig on the passage of substances from the blood of the mother into the foetus, in which he showed, in opposition to Gusserow, that iodine administered in solution to the parent speedily passes into the foetus.-M. Felix Kleim presented a contribution towards the interpretation of complex elements in geometry.-M. H. Hübner presented a paper by M. G. Spezia on the determination of iodine in the presence of chlorine, by means of protonitrate of thallium. This process is founded on the fact that whilst chloride of thallium is soluble in a large quantity of water, iodide of thallium is insoluble.-M. Wilhelm Weber communicated a paper by M. E. Riecke on the law of electro-organic reciprocal actions proposed by Helmholtz. -M. Clebsch exhibited and described two models prepared by M. Weiler, and relating to a particular class of surfaces of the

third order.

Sept. 18.-M. A. Clebsch read a paper on a new fundamental form of the analytical geometry of planes.

Sept. 25.-M. F. Kohlrausch presented a paper on the elec tromotive power of very thin strata of gas upon metal plates. Oct. 9.-M. A. Clebsch communicated a paper by M. A. Mayer on Lie's method of integration of the partial differential Oct. 30.-M. A. Clebsch communicated a long contribution by M. Sophus Lie to the theory of partial differential equations of the first order, and on their classification.

equations of the first order.

Nov. 13.-M. A. Clebsch presented a note by M. H. Grassmann on the theory of curves of the third order.-M. Weber communicated a paper by M. E. Reicke on the magnetisationfunction of a sphere of soft iron.-Prof. Henle presented a note by M. Oscar Grimm on the olfactory organ of the sturgeon, in which the author describes certain peculiar cells which occur on the surface of the olfactory grooves.-M. Oscar Grimm also ing to Häckel's Protistan group of the Catallacta, indicating a forwarded a note on Synura uvella and Uroglena volvox, belongprobable genetic connection of the Catallacta with the sponges.

VIENNA

Imperial Academy of Sciences, Oct. 10.-The completed MS. of a catalogue of observed Polar lights was forwarded by Dr. Herrmann Fritz of Zürich. Prof. Hlasiwetz communicated a memoir by Dr. F. Hinterberger on excretine. The substance was prepared by the author from fresh human excrement, and found to be free from sulphur and with the formula C20 H36 O. With bromine it forms bibromexcretine, with the formula C20 H34 Br2 O.-Dr. Kretschmar presented a memoir on the influence of morphine, and carbonate and sulphate of soda in diabetes mellitus. The first-mentioned substance acted beneficially, and reduced the secretion of sugar to zero.-Prof. L. Boltzmann communicated two memoirs, one containing further investigations on the heat-equilibrium among gaseous molecules, the other an experimental investigation on the behaviour of non-conducting bodies under the influence of electrical forces.

October 17.-M. Otto Hermann presented a memoir entitled "The Noble Siebenburgian Horse," intended to correct statements in Dr. L. J. Fitzinger's essay on the origin of the domestic horse and its races.-Prof. E. Mach, of Prague, communicated a memoir on the stroboscopic determination of musical notes. His stroboscopic scale is a uniformly rotating white cylinder covered with black longitudinal streaks, the closeness and number of which rapidly increases from one end of the cylinder to the other. This is observed through radiating fissures in a paper disc attached to the axis of the sirène, and the streaks are always seen simple at the spot where they pass before the eye in the vibration-number of the sirène.-The same author forwarded two papers prepared by him in conjunction with Dr. J. Kessel. In the first of these, on the function of the tympanic cavity and of the eustachian tube, the authors show by experiment, not only that the tuba is usually closed, but that this closure is necessary for the production of effective vibrations of the tym panic membrane. In the second they treat of the accommoda. tion of the ear, and show that, although alterations of the tension of the tensor tympani may cause a limited accommodation, such alterations do not occur in the living ear during hearing and listening.

Academy of Natural Sciences, May 28.-Frofessor Cope exhibited some vertebræ of a Plesiosauroid reptile and also those of a smaller species, probably a Clidasies which were found in close proximity near Sheridan, Kansas, by Mr. Joseph Savage, of Leavenworth. According to this gentleman, the vertebral column of the Clidastes was found immediately below that of the Plesiosauroid and in a reversed position, as though it had been swallowed by the latter or larger reptile. The largest vertebræ of the Clidastes were about three-quarters the length and one-fourth the diameter of those of the Plesiosauroid, and the animal must have furnished a large, or at least a long, mouthful for its captor. The bones of the Clidastes were not in good condition, but resembled those of C. cineriarum Cope, though smaller. The Plesiosauroid was new to science, being the third species discovered in the Cretaceous of the Niobrara group. Specifically it was nearest to the Elasmosaurus platyurus Cope, but was readily distinguished by the relatively shorter cervical vertebræ, and the regular acute ridges on the exterior surfaces near the margin of the articular faces, as well as the less contracted form of all the vertebral centra. Associated with these remains were those of a turtle of the size of some of the large Chelonide of recent seas. The only portions were the scapulo-procoracoid, the coracoid, and the mandible nearly complete. The general characters of this form were thought to agree with Cynocercus Cope, though the individual was larger than that on which the C. incisus was established.

June 4.-Mr. Thomas Meehan presented some specimens of the common asparagus, and remarked that in consequence of observing last year so many plants that had evidently flowered producing no seeds, he had this year examined them in a flowering condition and found them perfectly dioecious. Imperfect stamens existed in the female flowers, but they were never polleniferous. An occasional gynoecium in the male flower would make a weak attempt to produce a pistil, but no polleniferous flower ever produces a fruit. There was a great difference in the form of the male and female flowers. The former were double the length of the latter, and nearly cylindrical, while the female flower was rather campanulate. Other observers had nearly made the discovery of division in this plant. The old "English Botany" of Smith gave it the character of being occasionally imperfect, and the authors of "Deutchland's Flora considered it as occasionally polygamous. But Mr. Meehan was satisfied from a half day's investigation among many plants that in this region at least the asparagus is never perfect, but truly dicecious. He had observed another matter, small, but which might be of importance to systematic botanists, as well as to those engaged in evolutionary studies. One flower had a quadrifid stigma, and a four-celled ovary. The trinate type, or its multiple, is so closely associated with the endogenous structure, that he considered this circumstance particularly worthy of note. The male flowers seem very attractive to insects, various kinds of which seem to feed on the pollen. The honey bee was a frequent visitor. None seemed to be attracted to the female flowers. In the division into separate sexes the plant had gained nothing in the way of aid by insect fertilisation. Fertilisation seemed wholly accomplished by the wind. The male flowers are produced in much greater abundance than the female ones. Mr. Meehan added that this discovery had a more than usual practical importance. Many attempts had been made to improve the asparagus, as garden vegetables and the farm cereals had been improved; but it had often been questioned whether these improved forms would reprod ice themselves from seed as other garden varieties di 1. The tendency of thought the few past years had been in the direction of the belief that permanent varieties could be raised, and several improved kinds had been sent out by seedsmen, and were popular to a considerable extent. He said he had himself inclined to this opinion; but this discovery of complete diocism in asparagus, whereby two distinct individual forms were required to produce seed, rendered a true reproduction of one original parent impossible, as the progeny must necessarily partake of both forms.

"On the Fishes of the Ambyiacu River," by Edward D. Cope. The collection on which the present examination is based was made by our correspondent at Pebas, John Hauxwell. It embraces fishes of the small streams tributary to the Ambyiacu, as well as those of the river itself. The Ambyiacu is an inconsiderable river, which empties into the Amazon near to Pebas, in Eastern Equador, some distance east of the Napo. The results of the examination will be mentioned at the close of the list. As was to have been supposed, it consists almost exclusively of representatives of the three great families which abound in the neotropical region; the Chromidida, representing Physoclystous fishes, and the Characinidæ and Siluride, representing the Physostomi. The number of new species, 45 in a total of 74, constitutes a considerable addition to ichthyology, especially as the number of new generic forms is also rather large. The author adds a list of the species obtained by Robert Perkins, of Wilmington, Delaware, on a trip between Ucayale River. There are several interesting novelties in this the mouth of the Rio Negro and the Peruvian Amazon or collection, but their special localities are, unfortunately, not preserved. The specimens generally were large, and in fine condition.

BOOKS RECEIVED

ENGLISH.-A Budget of Paradoxes: A. De Morgan (Longmans).— Physics and Politics: W. Bagehot (H. S. King and Co).-Grotesque Animals: E. W. Cooke (Longmans)-Owens College Junior Course of Practical Chemistry: Roscoe and Jones (Macmillan).-The Hygiene of Air and Water: W. Procter (Hardwicke).

PAMPHLETS RECEIVED

ENGLISH.-The General Glaciation of Jar-Connaught and its Neighbourhood: Kinahan and Close. - Proceedings of the Geologists' Association, Vol. ii., No. 7.-Razi : W. Soleman.-Ninth Report of the Belfast Naturalists' Field Club.-The Curability of Cancer, 2nd edition -Introductory Lecture on Geology: E. Wilson-The Examination Questions in Geology, with answers-Transactions of the Institute of Engineers.-Annual Report of Vigilance Association.-A Catalogue of a Collection of Models of Ruled Surfaces, constructed by M. F. de Lagrange.-Journal of Anatomy and Physiology, No 2.-Weather Report of the Meteorological Office, JanuaryMarch, 1872-Transactions of the Clifton College Scientific Society, Part 3 -Journal of the Society of Telegraphic Engineers, No. 1.-Report of the Lower Mosely Street School Natural History Society.-Ocean Highways, Parts 1, 2.-A Table of the relative value of different Articles of Food: C. Ekin -The Advantages of Gas for cooking and heating: M. Ohren.Twelve Months' Experience with the A. B.C. Process of Purifying Sewage: W. Crookes.-Provident Knowledge Papers, Nos. 1-12.

AMERICAN AND COLONIAL.-Canadian Naturalist, vol. iv., Nos. 9-10.New Remedies: H. J. Wood, vol. ii., No. 2.-The Birds of Florida: C. J. Maynard, No. 1.-Proceedings of the American Philosophical Society, January June, 1871.-Deductive and Inductive Training: B. Silliman.-The Australian Mechanic, Nos. 8 and 9-Indiana Journal of Medicine for September. -Lippincott's Magazine for November.-Proceedings of the Asiatic Society of Bengal for August.

FOREIGN.-Sitzungsb. der geologischen Reichsanstalt zu Wien, No. 13.Zeitschrift für Meteorologie, Nos. 20-23.-Zeitschrift für Ethnologie, No. 21.-Le Physiometre: P. Harting.-Ofversigt af kongl. Vetenskaps Akad. Forhandlinger.-Bulletin de l'Acadèmie Royale de Belgique, Nos. 9 and 10. Sitzungsb. der k. k. Akad der Wiss. zu Wien, Nos. 24, 25.-Bulletin de la Societé de Geographie de Paris, September.

THURSDAY, JANUARY 2, 1873

THE GOVERNMENT AND THE ARCTIC EXPEDITION

ΤΗ 'HE Arctic Expedition is undoubtedly the question of the day; or, seeing that the wheels of the gods have brought us to the commencement of another annual round, it may be really called the question of the yearthat is, of the coming one. We may as well confess at once that we consider it quite worth all the attention it is likely to receive, either at the hands of Her Majesty's Ministers or from the public at large.

It is understood that the Government are at the present moment considering their decision, and it is because this is so that we venture to return to the subject, as there is an idea that the matter has not been put before the Government in the strong manner that it might have been; and the idea is true to a certain extent. But the blame, if any blame there be, attaches more to our scientific system, or rather our want of all system, than to any individuals. No doubt the Royal Society should have had a little more, and the Geographical Society a little less to say at the deputation that waited upon the Government, because we believe that the time has come when both Ministers and people will demand the widest possible basis of research for such an expedition; and that the widest possible basis was not put forward has since been clearly shown by Prof. Balfour Stewart, who has written to the Times on the subject. His letter is so important that we give it almost in extenso. He writes :"We have pursued terrestrial meteorology and magnetism now for some time, but until lately we have been rewarded with little apparent success. We are at last, however, beginning to understand the great importance of these studies, and to see the true path in which they ought to be pursued,

"Proofs of an intimate and mysterious connection between the sun and the earth are rapidly accumulating from various quarters, and the latest instance is one which is surely well worth the attention of all practical men. "I allude to the discovery by Mr. Charles Meldrum, of Mauritius, that the years when most spots are observed on the sun's surface are also those of most cyclones in the Indian Ocean. Furthermore, a similar connection between the state of the sun's surface and the magnetism of the earth was noticed twenty years ago by Sir Edward Sabine, the late president of the Royal Society.

"Now, surely we ought to inquire into the nature of this mysterious connection, and, if necessary, we ought to spend both means and trouble in the pursuit of such an inquiry?

"What, then, ought to be done? The line of action is surely that recently suggested by Mr. Norman Lockyer. We ought, in the first instance, to scrutinise the sun's surface with all the appliances we can command, with the view of recording the meteorological changes which are there occurring; and in the next instance we ought to do the same with regard to our own earth. To do the first it will be necessary to establish a proper physical observatory; and to do the second it is essential that we should become better acquainted with the less frequented regions of our globe, which are in many respects the most important. We must especially greatly extend our knowledge of the northern regions, and not of those alone but of the less frequented oceanic regions also. "Now, these are objects which can only be accomplished by means at the disposal of Government; for it will be in vain to expect whalers to supply us with the knowledge we desire of these northern regions, and it will be equally VOL. VI.-No. 166

in vain to expect merchantmen to cruise about in the less frequented oceanic latitudes in order to increase our acquaintance with their meteorology.

66

We have before us the splendid possibility of predicting the nature of seasons; but surely we cannot expect that Nature, who is usually so reticent, will disclose her secrets to a nation or a race who will not take reasonable trouble to complete their knowledge of the physics of the earth?”

Now there is no man of science who will gainsay these remarks coming from so distinguished an authority; and it is quite obvious that if the promoters of the expedition had taken a little more trouble and given a little more publicity to their action, the deputation might have been able to enforce its main arguments by this and other additional "reasons" given by other eminent men of science. Before it is too late, then, and another year is lost, it is to be hoped that the views so ably expressed by Dr. Stewart and held by all who have studied the subject in which he is such an acknowledged master, will be placed before the Government in the most forcible manner possible. The sun cycle to which he refers and which we now know governs cyclones and rainfall in certain parts of the earth, may it not also have something to say to the very passage to the Pole itself? May not the rainy mild seasons, which in the northern temperate zone, have more than once, to say the least, followed the sun-spot maximum, influence the dense masses of polar ice and make navigation more easy? If no one can answer this question, we have in this point alone a sufficient "reason" for undertaking the expedition; while the study of the whole phenomena including the spectrum of the aurora would furnish another, if the mere number of questions were to have weight; and it is curious to notice, that while we remain so ignorant of the nature of whole ranges of polar phenomena in the case of our own planet, the solar polar phenomena have recently been investigated by Prof. Respighi, with marvellous success, by means of the new method.

Sooner or later the polar phenomena of the earth must be studied, and their variations laid down in curves. Modern science demands this, and every year now lost it may take ten to recover. The question is, is England to have a hand in this matter? It is not a question between A's or B's pet theory of getting to the Pole. Will the Government refuse the expedition, now that Admiral Richards, the distinguished Hydrographer of the Admiralty, an officer in whose hands we may with safety leave the claims of cosmical science, has volunteered to command it? In the centuries to come, it will be told how England, in 1870 and 1871, sent out expeditions to observe eclipses of the sun, how in 1872 she sent out the Challenger, how in 1874 she sent out expeditions to observe the Transit of Venus. Why, then, should 1873 not be thus distinguished? We firmly believe that the Government have obtained a firmer hold upon the best side of Englishall their merely political measures; and surely a universal men by their aid to these scientific expeditions than by approval, separated as far as possible from a party feeling, is the best thing Government can strive to obtain.

We believe a statement that the Government has refused the expedition will be received with universal disappointment by every class of Englishmen, to whom the memories which dwell round the name of Captain Cook and a whole navy of Arctic explorers in the past are very dear and a source of pardonable pride.

K

the progrESS OF NATURAL SCIENCE DURING THE LAST TWENTY-FIVE YEARS

DU

II.

URING the last quarter of a century, the history of the formation of our earth has assumed a new aspect. When the Cosmos appeared, the opinion prevailed that our earth, once a globe of liquid fire, became covered with a crust of congealed scoriæ, on which, byand-by, the first animal and plant life made its appearance; after an almost infinite length of time, during which the Silurian, Devonian, Carboniferous, and Permian strata were deposited, a terrible catastrophe, affecting simulta

neously the whole earth, so completely destroyed the first palæozoic life, that not a single species survived the universal devastation. Upon the lifeless expanse, it was supposed, appeared then, forming the Secondary Fauna and Flora, entirely unconnected with and different from the extinguished one, until after frequent repetitions of the same process at longer or shorter intervals, man made his appearance, and along with him all existing plants and animals: with him begins the Historical Period, whose duration has not exceeded 6,000 years. The causes of these world-wide revolutions Geology sought in the violent reaction of the molten interior against the once extremely slender crust.

The ex

In opposition to these views,. the opinion peculiarly associated with the name of Lyell has made way, that no violent revolutions, returning at intervals, destroyed the external structure of the earth and all the life it sustained, but that all changes even in the earliest times affected only the earth's surface, and that these could only be the results of the same powers of nature which are actively at work on the earth at the present time; and that moreover, the gradual, but ever active powers of water, of air, and of chemical change, have perhaps had a greater share in accomplishing these transformations, than the fierce eat of subterranean masses of lava. plorers of the buried remains of plants and animals show it to be impossible that all life in those geological formations could have been destroyed simultaneously, for many species are common at several stages; in particular many existing animals and plants reach far back into the primitive world. Man himself could be shown to have been contemporary with many extinct species of plants and animals, and therefore his age on the earth must be extended back to an indefinite period. Man was witness to that inundation which buried the plains of the old and the new world under the waves of the sea of ice. Even in the immediately preceding period, when the subtropical elephant, rhinoceros, and hippopotamus disported themselves in the lignite woods of Middle Europe, have traces of mankind been found. Only in the most recent times has a foundation been laid for the pre-historic records of mankind, by means of which we may be able to obtain a knowledge of the state of civilisation, weapons, implements, and dwellings of that primitive

race.

No book of recent times, Dr. Cohn thinks, has influenced to such an extent the aspects of modern natural science, as Charles Darwin's work "On the Origin of Species," the first edition of which appeared in 1859. For even to so late a period, was the immutability of species believed in ; so long was it accepted as indubitable that all the characteristics

which belong to any species of plants and animals were transmitted unaltered through all generations, and were under no circumstances changeable; so long did the appearance of new fauna and flora remain one of the impenetrable mysteries of science. He who would not believe that new species of animals and plants, from the yeastfungus to the mammalia, had been crystallised parentless out of transformed materials was shut up to the belief that in primeval time an omnipotent act of creation, or, as it may be otherwise expressed, a power of nature at present utterly unknown, interfered with the regular progress of the world's development; yea, according to the researches of D'Orbigny and Elie de Beaumont, twenty-seven different acts of creation must have followed each other previous to the appearance of man-but after that, no more. It was Darwin who lifted natural science out of this dilemma, by advancing the doctrine that the animals and plants of the late geological eras no more appeared all at once upon the scene, than those of the preceding epochs simultaneously and suddenly disappeared; on the contrary, these are the direct descendants of former species, which gradually in the course of an exceedingly long period, through adaptation to altered conditions of life, through the struggle for existence, through natural and sexual selection have been changed into the new species. Professor Cohn does not doubt but that Darwin and his school may have over-estimated the reach of the explanations given by him to account for the transmutation of species, and especially the importance of natural and sexual selection, but the fundamental fact has been established, and will remain so for all future time. This fact is that the collective life of the earth, from the beginning even until now, and from the fungus-cell up to man, represent a single series which has never once been broken, whose members through direct propagation have proceeded out of each other, and in the course of a vast period have been developed into manifold and, on the whole, perfect forms.

The sciences which are concerned with life have during late years been cultivated on all sides; even in earlier years Cuvier and Jussieu had done as much for zoology and botany as the state of discovery in their time permitted, but since 1858 the boundaries of both kingdoms have been widely extended by the labours of Carpenter, Huxley, and Pourtalès.

After referring to the researches of Goethe in the last century, and those of Bauer and of Johannes Müller in the present, in reference to the physiology of plants and animals, Prof. Cohn says it was only in our own time, and first in 1843 in Schleiden's "Grundzügen der Wissenschaftlichen Botanik," that the new principle was followed out; the principle, namely, that all vegetable phenomena and all the various forms of plants proceed from the life and the development of their cells. After Schwann discovered that animal bodies also were built up from an analogous cell, mainly by Virchow was then developed from this principle the modern cellular physiology and pathology which traces the condition both of healthy and diseased men and animals back to the life-function of their cells, But, as the lecturer says, to attempt to follow out the advances made by science in these directions during the last twenty-five years would require a large volume, and cannot be done in the space of a lecture or an article.