decrement; a is the steady deflection due to unit current, and is the periodic time of the ballistic needle. Here a and are quantities very readily obtained. The chapter concludes with a full description of Dr. Hopkinson's "Bar and Yoke" method. Chapter IV. contains valuable information with regard to curves of induction and hysteresis in the case of wrought iron, steel, and cast iron, which will be of use to the electrical engineer in the design of dynamo electric machinery. The effects of annealing and stretching iron are brought forward and well illustrated. The next chapter, on magnetic hysteresis, is perhaps the most important in the book. It commences by giving a clear definition of hysteresis, the effects of which are amply illustrated by curves, and stress is laid upon the definition of permeability as being the ratio of B to H with certain limitations. The dissipation of energy through magnetic hysteresis --which plays such an important part in the design of cores for transformers, and the armatures of dynamos-is fully treated. The remarks on magnetic viscosity towards the end of the chapter are worthy of very careful consideration. The author points out that in the case of quick cycles, j HɗI may be widely different from what is found to be the case by static methods, and further remarks that experimental evidence is wanting under this head.1 Chapter VI. treats of magnetism in weak fields. The author refers to experiments by Lord Rayleigh and himself, in which the time effect upon magnetism is clearly shown-the creeping up of the magnetism going on for a considerable time. Magnetism in strong fields is discussed in Chapter VII. The "Isthmus Method" introduced by the author and Mr. W. Low in 1887 is capable of producing magnetic fields of enormous strength. In giving his conclusions from experiments by the isthmus method the author states, "there is apparently no limit to the value to which the induction may be raised. But, when we measure magnetisation by the intensity of magnetism I, we are confronted with a definite limit-a true satura tion value, which is reached or closely approached by the application of a comparatively moderate magnetic torce." A full account of Dr. Hopkinson's researches on the effect of temperature on magnetism is given in Chapter VIII., and reference is made to the identification of recalescence with recovery of the magnetic state. 1 For recent experiments upon Magnetic Viscosity see a paper by J. Hopkinson, F.R.S., and B. Hopkinson in Electrician, September 9, 1892. In the latter part of the chapter hysteresis, in the relation of magnetic susceptibility to temperature, is dealt with; and mention is made of the wide range of temperature through which the alloys of iron and nickel may exist in either the magnetic or nonmagnetic state. Reference is made to the researches on recalescence of Osmond, who has since shown the marked influence of the initial temperature, and the rate of cooling on recalescence in the case of chromium steel. Dr. Bottomley has shown that the alloys of chromium and steel in the unannealed state have exceptionally high magnetic qualities, which are confirmed by experiments of Dr. Hopkinson. In Chapter X. the magnetic circuit is discussed, and the way in which it is applied to the design of dynamo electric machines and transformers. Reference is made to the important work of Drs. J. and E. Hopkinson and Kapp upon this subject- more especially in connection with dynamo electric machinery. In pursuing the analogy of the magnetic circuit to the ordinary conduction equation, Prof. Ewing lays stress upon the fact that the permeability (μ) is a function of the induction (B), and this is a point which cannot be too strongly urged. Much that is in this chapter has great practical importance-the treatment of the subject being considered from a graphical, as well as analytical, point of view. The chapter ends with an account of the influence upon magnetism by cuttings and the compression of joints in magnetic circuits. The last chapter gives a complete account of the different theories of magnetism. Weber's theory is discussed with modifications by Maxwell and Wiedemann, to which are added Prof. Ewing's own views of the subject. He goes on to show that the reduction of hysteresis by vibration is explained by the molecular theory of magnetism, and further supposes that timelag in magnetism can be accounted for by it. The book ends with an account of Ampère's hypothesis of magnetic molecules. E. WILSON. OUR BOOK SHELF. Forschungsberichte aus der Biologischen Station zu Plön. Theil I. Faunistische und biologische Beobachtungen am Gr. Plöner See. Von Dr. Otto Zacharias, Direktor der Biologischen Station. (Berlin: R. Friedländer und Sohn, 1893.) THE first report of investigations from the biological station of Plön, in Holstein, has just been issued. It is a journal of 52 pages with one plate, bearing on the front of the cover a neat representation of the turreted three-storey building reflected in the quiet waters of the inland lake, and on the back a list of the regulations observed in the management of the station. In his introductory remarks the Director, who has already made his views known with regard to the importance of freshwater laboratories in the pages of several German scientific periodicals, gives a brief sketch of the advance already made in this direction in Italy, France, and America. The first paper gives a list of the fauna at present known to inhabit the lake. This occupies seven pages; and fourteen names, being printed in italics, signify that they are new to science. The new species and genera are treated in detail in the second paper. The greatest number occur amongst Rotateria, but additions are also made to the Rhizopods, Heliorea, and Infusoria. No new forms appear to have been found amongst the crustacea, mollusca, or fishes. A third paper deals with the distribution and special natural history of the forms met with, and with the comparison of the plankton at different seasons. There are no foot-notes through the number, but all references to literature are formed into a numbered table at the end. The plate, which is one of Klinkhardt's, of Leipzig, shows a number of the new forms discovered. The investigations are almost entirely on the minute floating organisms, as must necessantly be the case at this date with all freshwater work not connected directly with pisciculture. The British Journal Photographe Aminic for 180g, Edited by J. Trail Taylor London. Henry Green wood, and Co., 1898.) it was not an ordinary glow-worm, with which she is perfectly familiar; and, moreover, she called the attention of a cousin to the creature at the time, who corroborates her account. Are there worms in England capable of emitting light besides the glow-worm? If so, are they at all common?" In reply to a series of questions, I was able to elicit these further particulars :-" It was in a garden in the village of Lorg September last [1892], or the beginning of October. My sister's Wittenham, near Didcot, on a dark evening in the latter part of attention was attracted by the light on the ground, and she picked the worm up. While she cannot positively assert that she saw it in motion on the ground, it certainly wriggled in her band. For a few seconds also after putting it down her fingers remained phosphorescent." The notice of the public, so far as I have been able to ascer tain, was first directed to this phenomenon among earthworms by Grimm in 1670, but scientific observation, as we now understand it, was then scarcely known. A century elapsed before any further record was made in the periodicals of Europe which I have consulted, then came a paper by Flaugergues in 1781. This article, which appeared in Lichtenberg's magazine, was THIS annual volume contains as usca a rast amount written in German. In 1873 Cohn's observations on the same of useful information gathered from workers in the subject were published in the well-known Zeitschrift für Wis various applications of photography. After a dret sum-sensch. Zool., while numerous recent writers have further conmary, in which the editor reters to some of the chief tributed to our knowledge, especially in relation to the Conadvances made in the science of photograhy Zong the | tinental species. past year, mentioning, for instancɛ. Mz. Da meyer's telephotographic lens, Mr. W is's marreement in the p'atinotype process, &c., he devotes a few pages to some photographic methods of book lustration Then come short contributions in which everyone has something special to say, whether it relates to a new mounting medium, a permanent toning bath, or nir hole pictures, &c. They are far too numerous to menzor individus het be found most interesting reading Digitame at Press" is the title of a series of notes be Mr. Trailer, in which he refers brief! and it some cases at length, to new methods, remedies. &c. 950 instri mends used in the practice of the ari The farmoig and tables are as numerous as ever, while al the other formation, such as lists of photographi sanie ies do, have been brought V. to date. The same a 23906Y astrated. ཟླ་ ༧༩༧སངས་༧ Stuns has here mete 0 less that hemanth, extended tran Septembe Warren Barry, M.A. the first visit being has thus hac Thus in 1872 an article appeared in the French Annals of Natural Science, by Panceri, entitled "Studies in the Fhosphorescence of Marine Animals, in which he states that the luminosity observed in the case of certain (earth) worms is die that by the evolution of light there was no perceptible raising of to a secretion from the girdle, where special glands exist, and the temperature. In this respect, therefore, the earthworm's glow corresponds with that emitted by the firefly, Noctilucz and glow-worm. One investigator at least has tested the colear and composition of the luminosity by the spectroscope, and says that it is not uni-coloured or monochromatic, but compounded chiefly of the red and violet rays. Other students regard the substance which produces the light as homogeneous. In 1838 Eversmann published an article on a night-shining worm in Russian, and in 1871.an English naturalist named Breese delivered an address on the earthworm before the West Kea Natural History Society, from a meagre abstract of which we learn that he had spent some years on the subject of anneli luminosity, having studied it historically from the year 1805. when Viviani wrote on the phosphorescence of the sea, down to the date of his own delivery. According to Breese the lum nosity exists in the excreted glutinous material with which the outer skin of the animal is covered. More than one creature has at different times borne the name of the phosphorescent worm. In 1837 Dages, a French writer. described a species under this name (Larios plosphoreus. with a girdle extending from the 13th to the 16th segments, at! a somewhat flattened body behind. After the lapse of exactly half a century this curious creature was examined again, 13. named by Giard Photodrilus, or the luminous worm. It bas | eight setæ, just as our common species have, but they are | separate, and not in couples. There is no gizzard, nor does the lip dovetail into the segment behind. It is a small, transparent, rose-coloured worm, and decidedly phosphorescent. In 1843 when the British Association met at Cork, specimens of an annelid were exhibited by Dr. Allman, which he had i covered in the bogs of the south of Ireland, and which was cause of a luminous appearance. When irritated the worm gave out a phosphorescent light, which is said to have been much creased by exposing the creature to the vapour of alcohol. light was of that peculiar soft greenish hue which is characte istic of the phosphoresence observed in light-giving anima and familiar to most readers in connection with the glowAnother gentleman was reported to have observed the sum peculiarity in some annelids which exist in the bogs of Cornaught. I have been unable to find any recent reference to confirmation of these curious observations. Ten years ixter MHenry Cox exhibited an earthworm which was phosphoresc at a meeting of the Literary and Philosophical Society of Lar pool, held November 14, 1853. While few records of a trustworthy nature respecting the ober vation of luminous worms in Britain are available, a good den is been done by our Continental fellow-workers Ve who wrote a very valuable work on the various species of nelids in 1884, gives us some results of his personal experience, which I believe have never been placed before the English reader. He says that he had the good fortune once at least to observe an interesting case of phosphoresence in connection with the brandling. It was one warm July night in the year 1881, when he was exploring a dung-heap. Naturalists do not usually work with kid gloves and diamond rings. Presently a spot of soft, bluish-white light appeared, which, however, was changeful and unsteady. Now it would disappear, then return anew and shine forth over a larger space, though never with a brilliant hue. He thereupon removed a portion of the manure from the spot where he had observed the luminosity, and found that the light appeared brighter, and shone for a longer time without disappearing, or before it migrated to another spot. By means of a lantern Vejdovsky was able to secure a large number of specimens of the brandling from the dung-heap, which he placed in a vessel for the purpose of subjecting them to careful observation. To his great surprise he found that his finger soon glowed in the darkness with the phosphorescence, which extended generally over the hand where it came into contact with the worms. It was therefore apparent that the luminosity was the product of a fluid secreted by the cutaneous glands, which had attached itself to the hand of the investigator, and now manifested itself in this curious way. We have an interesting observation on the same subject by Prof. von Stein, which was published at Leipzig in 1883. One evening in the middle of September the Professor was spending some time with a circle of friends at a parsonage not far from Potsdam, when the conversation turned upon phosphorescence and the phenomena of light. Hereupon one of the younger members of the family-who are usually the keenest and most shrewd observers of Nature, and the best friends of the naturalist -observed that there were fountains in the adjoining gardens, the water from which was frequently observed to be full of light-bearing creatures when it was violently agitated. He regarded the affair at first simply as a hoax, or an attempt to make a fool of him-as people are ever ready to do with a hobby-rider -but ascertained eventually that the luminosity was due to the presence of a species of worm which possessed the property of shining when disturbed. As with Vejdovsky, so with Prof. von Stein, the finger which had come into contact with the worm continued to glow for some time after. What species of worm was under observation is not recorded. It now becomes a question, What end could be served thereby? The philosopher no sooner learns a new fact than he begins to pry into the secret which lies beneath, and stands to it as cause to effect. We have analogy to guide us. The water worms may be compared with the marine animals which produce phosphorescence, while the brandling may be studied in the light of the glow-worm. It may be objected that as worms have no eyes there can be no advantage in their luminosity. But such an argument would be based on the erroneous assumption that a creature without eyes is incapable of receiving impressions from light. That worms are influenced by light is proved both by their habit of avoiding light, and by the experiments which have been carried out by various students. Darwin remarks that as worms are destitute of eyes he at first thought they were quite insensible to light. He found, however, that "light affects worms by its intensity and by its duration." Hoffmeister states that with the exception of a few individuals worms are extremely sensitive to light, and from my own observations I have been able to demonstrate that there are marked differences in the susceptibility of the different species-some being very much more susceptible than others. Now it follows that if a number of species of worms lived together in one place, as they usually do in a manure heap, it would be a great advantage for a given species to possess a distinguishing feature, such as that of luminosity, to enable two individuals to discover each other's whereabouts, just as the male glow-worm detects the female by the light emitted from her upturned abdomen. We have, moreover, the fact that certain species of earthworm are characterised by a peculiar odour, which must be of great service in preventing promiscuous copulation and hybridity. Though earthworms are destitute of nasal organs they can detect odours, and though sightless they are affected by light. Viewed in this light a new field of research is opened up which hitherto has been totally unworked, but which may be hoped to yield remarkable results if diligently, patiently, and intelligently tilled. It would be an easy thing for any one living in the country, with access to an old manure heap, where the brandling (Allolobophora fætida, Sav.) usually abounds, to ascertain whether such luminosity is of common occurrence, and it would be exceptionally valuable to record the period of the year, the state of the atmosphere, the age of the moon, and other data which would enable the specialist to arrive at a satisfactory conclusion. I shall be glad to receive communications, addressed "The Grove, Idle, Bradford," from observers who may find pleasure in such pursuits. HILDERIC FRIEND. Quaternions and the Algebra of Vectors. IN a recent number of this Journal (p. 151) Mr. McAulay puts certain questions to Mr. Heaviside and to me, relating to a subject of such importance as to justify an answer somewhat at length. I cannot of course speak for Mr. Heaviside, although I suppose that his views are not very different from mine on the most essential points, but even if he shall have already replied before this letter can appear, I shall be glad to add whatever of force may belong to independent testimony. Mr. McAulay asks: "What is the first duty of the physical vector analyst qua physical vector analyst ?" The answer is not doubtful. It is to present the subject in such a form as to be most easily acquired, and most useful when acquired. In regard to the slow progress of such methods toward recognition and use by physicists and others, which Mr. McAulay deplores, it does not seem possible to impute it to any want of uniformity of notation. I doubt whether there is any modern branch of mathematics which has been presented for so long a time with a greater uniformity of notation than quaternions. What, then, is the cause of the fact which Mr. McAulay and all of us deplore? It is not far to seek. We need only a glance at the volumes in which Hamilton set forth his method. No wonder that physicists and others failed to perceive the possibilities of simplicity, perspicuity, and brevity which were contained in a system presented to them in ponderous volumes of 800 pages. Perhaps Hamilton may have intended these volumes as a sort of thesaurus, and we should look to his shorter papers for a compact account of his method. But if we turn to his earlier papers on Quaternions in the Philosophical Magazine, in which principally he introduced the subject to the notice of his contemporaries, we find them entitled "On Quaternions; or on a New System of Imaginaries in Algebra," and in them we find a great deal about imaginaries, and very little of a vector analysis. To show how slowly the system of vector analysis developed itself in the quaternionic nidus, we need only say that the symbols S, V, and v do not appear until two or three years after the discovery of quaternions. In short, it seems to have been only a secondary object with Hamilton to express the geometrical relations of vectors, secondary in time, and also secondary gin this, that it was never allowed to give shape to his work. But this relates to the past. In regard to the present status, I beg leave to quote what Mr. McAulay has said on another occasion (see Phil. Mag. June, 1892):-"Quaternions differ in an important respect from other branches of mathematics that are studied by mathematicians after they have in the course of years of hard labour laid the foundation of all their future work. In nearly all cases these branches are very properly so called. They each grow out of a definite spot of the main tree of mathematics, and derive their sustenance from the sap of the trunk as a whole. But not so with quaternions. To let these grow in the brain of a mathematician, he must start from the seed as with the rest of his mathematics regarded as a whole. He cannot graft them on his already flourishing tree, for they will die there. They are independent plants that require separate sowing and the consequent careful tending.' Can we wonder that mathematicians, physicists, astronomers, and geometers feel some doubt as to the value or necessity of something so separate from all other branches of learning? Can that be a natural treatment of the subject which has no relations to any other method, and, as one might suppose from reading some treatises, has only occurred to a single man? Or, at best, is it not discouraging to be told that in order to use the quaternionic method, one must give up the progress which he has already made in the pursuit of his favourite science, and go back to the beginning and start anew on a parallel course? I believe, however, that if what I have quoted is true of vector methods, it is because there is something fundamentally wrong in the presentation of the subject. Of course, in some sense and to some extent it is and must be true. Whatever is special, accidental, and individual, will die, as it should; but that which is universal and essential should remain as an organic part of the whole intellectual acquisition. If that which is essential dies with the accidental, it must be because the accidental has been given the prominence which belongs to the essential. For myself, I should preach no such doctrine to those whom I wish to convert to the true faith. In Italy, they say, all roads lead to Rome. In mechanics, kinematics, astronomy, physics, all study leads to the consideration of certain relations and operations. These are the capital notions; these should have the leading parts in any analysis suited to the subject. If I wished to attract the student of any of these sciences to an algebra for vectors, I should tell him that the fundamental notions of this algebra were exactly those with which he was daily conversant. I should tell him that a vector algebra is so far from being any one man's production that half a century ago several were already working toward an algebra which should be primarily geometrical and not arithmetical, and that there is a remarkable similarity in the results to which these efforts led (see Proc. A. A. A. S. for 1886, pp. 37, ff.). I should call his attention to the fact that Lagrange and Gauss used the notation (aẞy) to denote precisely the same as Hamilton by his S(aßy), except that Lagrange limited the expression to unit vectors, and Gauss to vectors of which the length is the secant of the latitude, and I should show him that we have only to give up these limitations, and the expression (in connection with the notion of geometrical addition) is endowed with an immense wealth of transformations. I should call his attention to the fact that the notation [], universal in the theory of orbits, is identical with Hamilton's V(PIP), except that Hamilton takes the area as a vector, i.e. includes the notion of the direction of the normal to the plane of the triangle, and that with this simple modification (and with the notion of geometrical addition of surfaces as well as of lines) this expression becomes closely connected with the first-mentioned, and is not only endowed with a similar capability for transformation, but enriches the first with new capabilities. In fact, I should tell him that the notions which we use in vector analysis are those which he who reads between the lines will meet on every page of the great masters of analysis, or of those who have probed deepest the secrets of nature, the only difference being that the vector analyst, having regard to the weakness of the human intellect, does as the early painters who wrote beneath their pictures "This is a tree, "This is a horse." I cannot attach quite so much importance as Mr. McAulay to uniformity of notation. That very uniformity, if it existed among those who use a vector analysis, would rather obscure than reveal their connection with the general course of modern thought in mathematics and physics. There are two ways in which we may measure the progress of any reform. The one consists in counting those who have adopted the shibboleth of the reformers; the other measure is the degree in which the community is imbued with the essential principles of the reform. I should apply the broader measure to the present case, and do not find it quite so bad as Mr. McAulay does. Yet the question of notations, although not the vital question, is certainly important, and I assure Mr. McAulay that reluc tance to make unnecessary innovations in notation has been a very powerful motive in restraining me from publication. Indeed my pamphlet on "Vector Analysis," which has excited the animadversion of quaternionists, was never formally published, although rather widely distributed, so long as I had copies to distribute, among those who I thought might be interested in the subject. I may say, however, since I am called upon to defend my position, that I have found the notations of that pamphlet more flexible than those generally used. Mr. McAulay, at least, will understand what I mean by this, if I say that some of the relations which he has thought of sufficient importance to express by means of special devices (see Proc. R. S. E., for 1890-91), may be expressed at least as briefly in the notations which I have used, and without special devices. But I should not have been satisfied for the purposes of my pamphlet with any notation which should suggest even to the careless reader any connection with the notion of the quaternion. For I confess that one of my objects was to show that a system of vector analysis does not require any support from the notion of the quaternion, or, I may add, of the imaginary in algebra. I should hardly dare to express myself with so much freedom. if I could not shelter myself behind an authority which will not be questioned. I do not see that I have done anything very different from what the eminent mathematician upon whom Hamilton's mantle has fallen has been doing, it would seem, unconsciously Contrast the system of quaternions, which he has described in his sketch of Hamilton's life and work in the North British Review for September, 1866, with the system which he urges upon the attention of physicists in the Philosophical Magazin in 1890. In 1866 we have a great deal about imaginaries, and nearly as much about the quaternion. In 1890 we have nothing about imaginaries, and little about the quaternion. Prof. Tai has spoken of the calculus of quaternions as throwing off in the course of years its early Cartesian trammels. I wonder that be does not see how well the progress in which he has led may be described as throwing off the yoke of the quaternion. A characteristic example is seen in the use of the symbol v Hamilton applies this to a vector to form a quaternion, Taito form a linear vector function. But while breathing a new lif: into the formula of quaternions, Prof. Tait stands stoutly by the letter. Now I appreciate and admire the generous loyalty toward one whom he regards as his master, which has always led Prof. Tait to minimise the originality of his own work in regard to quaternions, and write as if everything was contained in the ideas which flashed into the mind of Hamilton at the classic Brougham Bridge. But not to speak of other claims of historical justice, we owe duties to our scholars as well as to our teachers, and the world is too large, and the current of modern thought is too broad, to be confined by the ipse dixit even of a Hamilton. J. WILLARD GIBыr. Glacial Drift of the Irish Channel. It seems of interest to record that the eurite or microgranite containing blue amphibole (Riebeckite), the rock noticed by Mr. P. F. Kendall in the drifts of the Isle of Man and Caerna vonshire, occurs abundantly in the form of small pebbles on the shore at Killiney, co. Dublin, doubtless derived from the "glacial gravels" of the coast. I have also found a pebble in the raised beach at Greenore, co. Down. Mr. Teall's description of the rock of Ailsa Craig (Miner ogical Magazine, vol. ix. p. 219) enabled the very characteristic pebbles collected by Mr. Kendall to be referred to that mass as a source, or to formerly existing bosses south of or adjacent to it. As far as I am aware, all the material is in the form of pebbles often only an inch in diameter. This is hardly likely to be its original condition, if removed by ice from Ailsa Craig, and s only one of many points that indicate a redistribution of our socalled "glacial beds by subsequent action of rivers or other GRENVILLE A. J. COLE Science for Ireland, Dublin, March 12. waters. Royal College of THE SACRED NILE. THAT Egypt is the gift of the Nile is a remark we owe to the father of history, who referred not only to the fertilising influence of the stream, but to the fact tha the presence of the Nile and its phenomena are the conditions upon which the habitability of Egypt als gether depends. That that part of Egyptian archæology and myth which chiefly interests astronomers is also the gift of the Nile is equally true. The heliacal rising of Sirius and other stars at the time of the commencement of the inundations each year: 1 the myths which grew out of the various symbols of the stars so used, are so many evidences of the large share the river, with its various water levels at different times, had in the national life. It was, in fact, the true and unique basis of the national life. In this the Nile had a compeer, or even comper What the Nile was to Egypt the Euphrates and Tig were to a large region of Western Asia, where also we find the annual flood to have been in ancient times source of fertility over an enormous area which is now desert, the plains being broken by the remains of the ancient canals. What more natural than that Euphrates, Tigris and Nile were looked upon as deities; that the Gods of the Nile valley on the one hand, and of the region watered by the Euphrates and Tigris on the other, were gods to swear by; that they were worshipped in order that their benign influences might be secured, and that they had their local shrines and special cults. The god sacred to the Euphrates and Tigris was called Ea. The god sacred to the Nile was called Hapi. The name Hapi is the same as that of the bull Apis, the worship of which was attributed to Mena.1 Certainly Mena, Mini, or Menes, as he is variously called, was fully justified in founding the cult of the river god, for he first among men appears to have had just ideas of irrigation; and I have heard the distinguished officers who have lately been responsible for the irrigation system of to-day speaking with admiration of the ideas and works of Menes. Whether the Tigris had a Menes in an equally early time is a point on which history is silent; but, according to the accounts of travellers, the Tigris in flood is even more majestic than the Nile, and yet the latter river in flood is a sight to see a whole fertile plain turned into, as it were, an arm of the sea, with here and there an island, which on inspection turns out to be a village, the mud houses of which too often are undermined by the lapping of the waves in the strong north wind. There is no doubt that the dates of the rise of these rivers not only influenced the national life but even the religions of the dwellers on their banks. The Euphrates and Tigris rise about the time of the spring equinox-the religion was equinoxial, the temples were directed to the east. The Nile rises at a solstice-the religion was solstical and the solar temples were directed no longer to the east. To the Egyptians the coming of the river to the parched land was as the sunrise chasing the darkness of the night; the sun-god of day conquering the stargods of night; or again the victorious king of the land slaughtering his enemies. By no one, perhaps, have the impressions produced by the various phases of the river been so poetically described as by Osburn, a writer of vivid imagination, but it must be added that the facts detailed in his description are not exactly capable of being verified by engineering science. Osburn thus describes the low Nile: "The Nile has shrunk within its banks until its stream is contracted to half its ordinary dimensions, and its turbid, slimy, stagnant waters scarcely seem to flow in any direction. Broad flats or steep banks of black, sunbaked Nile mud, form both the shores of the river. All beyond them is sand and sterility; for the hamseen, or sand-wind of fifty days' duration, has scarcely yet ceased to blow. The trunks and branches of trees may be seen here and there through the dusty, hazy, burning, atmosphere, but so entirely are their leaves coated with dust, that at a distance they are not distinguishable from the desert sand that surrounds them. It is only by the most painful and laborious operation of watering that any tint approximating to greenness can be preserved at this season even in the pleasure-gardens of the Pacha. The first symptom of the termination of this most terrible season is the rising of the north wind (the Etesian wind of the Greeks), blowing briskly, often fiercely during the whole of the day. The foliage of the groves that cover Lower Egypt is soon disencumbered by it of the dust, and resumes its verdure. The fierce fervours of the sun, then at his highest ascension, are also most seasonably mitigated by the same powerful agency, which prevails for this and the three following months throughout the entire land of Egypt." Maspero, "Hist. Anc." xi. 10 Then at last comes the inundation : Perhaps there is not in Nature a more exhilarating sight, or one more strongly exciting to confidence in God, than the rise of the Nile. Day by day and night by night, its turbid tide sweeps onward majestically over the parched sands of the waste, howling wilderness. Almost hourly, as we slowly ascended it before the Etesian wind, we heard the thundering fall of some mud-bank, and saw by the rush of all animated Nature to the spot, that the Nile had overleapt another obstruction, and that its bounding waters were diffusing life and joy through another desert. There are few impressions I ever received upon the remembrance of which I dwell with more pleasure than that of seeing the first burst of the Nile into one of the great channels of its annual overflow. All Nature shouts for joy. The men, the children, the buffaloes, gambol in its refreshing waters, the broad waves sparkle with shoals of fish, and fowl of every wing flutter over them in clouds. Nor is this jubilee of Nature confined to the higher orders of creation. The moment the sand becomes moistened by the approach of the fertilising waters, it is literally alive with insects innumerable. It is impossible to stand by the side of one of these noble streams, to see it every moment sweeping away some obstruction to its majestic course, and widening as it flows, without feeling the heart to expand with love and joy and confidence in the great Author of this annual miracle of mercy." The effects of the inundation, as Osburn shows in another place, "exhibit themselves in a scene of fertility and beauty such as will scarcely be found in another country at any season of the year. The vivid green of the springing corn, the groves of pomegranate trees ablaze with the rich scarlet of their blossoms, the fresh breeze laden with the perfumes of gardens of roses and orange thickets, every tree and every shrub covered with sweet-scented flowers. These are a few of the natural beauties that welcome the stranger to the land of Ham. There is considerable sameness in them, it is true, for he would observe little variety in the trees and plants, whether he first entered Egypt by the gardens of Alexandria or the plain of Assouan. Yet is it the same everywhere, only because it would be impossible to make any addition to the sweetness of the odours, the brilliancy of the colours, or the exquisite beauty of the many forms of vegetable life, in the midst of which he wanders. It is monotonous, but it is the monotony of Paradise." "The flood reaches Cairo on a day closely approximating to that of the summer solstice. It attains its greatest height, and begins to decline near the autumnal equinox. By the winter solstice the Nile has again subsided within its banks and resumed its blue colour. Seed-time has occurred in this interval. The year in Egypt divides itself into three seasons-four months of sowing and growth, corresponding nearly with our November, December, January, and February; four months of harvest from March to June; the four months of the inundation completing the cycle." In order to show how the astronomy of the ancient Egyptians to deal specially with them-was to a large extent concerned with the annual flood and all that depended upon that flood, and how the first solar year used on this planet, so far as we know, was established, it is important to study the actual facts of the rise somewhat closely, not only for Egypt generally, but for several points in the line some thousand miles in extent, along which in the earliest times cities and shrines were dotted here and there. Time out of mind the fluctuations in the height of the river have been carefully recorded at different points along the river. In the "Description de l'Egypt" we find a full description of the so-called nilometer at Assuan (First Cataract) which dates from a remote period, perhaps as early as the 5th Dynasty. In Ebers' delightful book on Egypt space is given to |