« PreviousContinue »
number occur amongst Rotatoria, but additions are also it was not an ordinary glow-worm, with which she is perfectly made to the Rhizopods, Heliozoa, and Infusoria. No new familiar; and, moreover, she called the attention of a cousin forms appear to have been found amongst the crustacea, to the creature at the time, who corroborates her account. An mollusca, or fishes.
there worms in England capable of emitting light besides be A third paper deals with the distribution and special
glow-worm ? If so, are they at all common?” natural history of the forms met with, and with the com
In reply to a series of questions, I was able to elicit these parison of the plankton at different seasons.
further particulars :-" It was in a garden in the village of Long There are no foot-notes through the number, but all
Wittenham, near Didcot, on a dark evening in the latter part de
September last (1892), or the beginning of October. My sister's references to literature are formed into a numbered table
attention was attracted by the light on the ground, and she at the end. The plate, which is one of Klinkhardt's, of picked the worm up. While she cannot positively assert that Leipzig, shows a number of the new forms discovered. she saw it in motion on the ground, it certainly wriggled in her
The investigations are almost entirely on the minute hand. For a few seconds also after putting it down her fingers floating organisms, as must necessarily be the case at remained phosphorescent." this date with all freshwater work not connected directly The notice of the public, so far as I have been able to ascerwith pisciculture.
tain, was first directed to this phenomenon among earthworss
by Grimm in 1670, but scientisic observation, as we now uodeThe British Journal Photographic Almanac for 1893. stand it, was then scarcely known. A century elapsed before
Edited by J. Traill Taylor. (London : Henry Green- / any further record was made in the periodicals of Europe which wood, and Co., 1893.)
I have consulted, then came a paper by Flaugergues in 1781 This annual volume contains, as usual, a vast amount
This article, which appeared in Lichtenberg's magazine, #23
written in German. In 1873 Cohn's observations on the same of useful information gathered from workers in all the subject were published in the well-known Zeitschrift für Hivarious applications of photography. After a brief sum sensch. Zool., while numerous recent writers have further de mary, in which the editor refers to some of the chief / tributed to our knowledge, especially in relation to the Cosa advances made in the science of photography during the tinental species. past year, mentioning, for instance, Mr. Dallmeyer's Thus in 1872 an article appeared in the French Annak cí telephotographic lens, Mr. Willis's improvement in the Natural Science, by Panceri, entitled “Studies in the Das p'atinotype process, &c., he devotes a few pages to “ some | phorescence of Marine Animals,” in which he states ibat ik photographic methods of book illustration.” Then come
luminosity observed in the case of certain (earth) worms is da: short contributionsin which everyone has something special
to a secretion from the girdle, where special glands exist, as to say, whether it relates to a new mounting medium, a per
that by the evolution of light there was no perceptible raising of
the temperature. In this respect, therefore, the earthwora's manent toning bath, or pinhole pictures, &c. They are far glow corresponds with that emitted by the firefly, Noculta. too numerous to mention individually, but will be found
and glow-worm. One investigator at least has tested the calca most interesting reading. “Epitome of Progress” is the and composition of the luminosity by the spectroscope, and says title of a series of notes by Mr. Traill Taylor, in which that it is not uni-coloured or monochromatic, but compoandes he refers briefly, and in some cases at length, to new chiefly of the red and violet rays. Other students regard te methods, remedies, &c., and instruments used in the substance which produces the light as homogeneous. practice of the art. The formulæ and tables are as In 1838 Eversmann published an article on a night shing numerous as ever, while all the other information, such
worm in Russian, and in 1871an English naturalist named Breeze as lists of photographic societies, &c., have been brought
delivered an address on the earthworm before the West Kea up to date. The volume is copiously illustrated.
Natural History Society, from a meagre abstract of which
learn that he had spent some years on the subject of annda Studies in Corsica. By John Warren Barry, M.A. luminosity, having studied it historically from the year 1805 (London : Sampson Low, Marston, and Co., 1893.)
when Viviani wrote on the phosphorescence of the sea, down?
the date of his own delivery. According to Breese the lasi MR. BARRI has twice visited Corsica, the first visit being
rsica, the first visit being nosity exists in the excreted glutinous material with which the of less than five months' duration, while the second outer skin of the animal is covered. extended from September 1882 to February 1885. He More than one creature has at different times borne the out" has thus had ample opportunities for the study both of the phosphorescent worm. In 1837 Dugès, a French write". of the island and of its people, and in the present described a species under this name (Lumbricus phosphares volume he sums up his impressions very brightly and with a girdle extending from the 13th to the 16th segments, a pleasantly. Most readers will probably like best the
a somewhat flattened body behind. After the lapse of execut chapters on life at Ajaccio, but they will also find much
half a century this curious creature was examined again. 2* to interest them in what the author has to say about the
nained by Giard Photodrilus, or the luminous worm. It Bush of Corsica and of the Mediterranean region.
eight setæ, just as our common species have, but they separate, and not in couples. There is no gizzard, nor does ** lip dovetail into the segment behind. It is a small, transparen'.
rose-coloured worm, and decidedly phosphorescent. LETTERS TO THE EDITOR.
In 1843 when the British Association met at Cork, specimet
of an annelid were exhibited by Dr. Allman, which he bad de [The Editor does not hold himself responsible for opinions ex covered in the bogs of the south of Ireland, and which was pressed by his correspondents. Neither can he undertake
cause of a luminous appearance. When irritated the worm gun to return, or to correspond with the writers of, rejected
out a phosphorescent light, which is said to have been muck manuscripts intended for this or any other part of NATURE.
creased by exposing the creature to the vapour of alcohol. 1 No nolice is taken of anonymous communications. ]
light was of that peculiar soft greenish hue which is characte Luminous Earthworms.
istic of the phosphoresence observed in light-giving a300."
and familiar to most readers in connection with the glow-wors I HAVE recently received from a correspondent a statement Another gentleman was reported to have observed the same which is sufficiently valuable to crave public attention. It opens peculiarity in some apnelids wbich exist in the boys of C up withal a very fascinating field of investigation, and one naught. I have been unable to find any recent reference * which, though it has by no means been altogether neglected by confirmation of these curious observations. Ten years later foretime naturalists, is as yet far from being fully understood. Henry Cox exhibited an earthworm which was phospborec
Writing from Richmond, Surrey, the Rev. Alfred Geden, at a meeting of the Literary and Philosophical Society of LR M.A., says :-"I have just heard of a phenomenon in the worm pool, held November 14, 1853. world which is new to me . . . My sister declares that one day While few records of a trustwortby nature respecting the be last summer, in a village on the Thames, she saw a phos. vation of luminous worms in Britain are available, a good deal phorescent worm,' and describes the creature as about one and been done by our Continental fellow-workers. Vejdons." a half inches long, worm-like in all respects. My sister is sure who wrote a very valuable work on the various species of
nelids in 1884, gives us some results of his personal experience, It would be an easy thing for any one living in the country, which I believe have never been placed before the English with access to an old manure heap, where the brandling (Alloloreader. He says that he had the good fortune once at least to bophora fætida, Sav.) usually abounds, to ascertain whether such observe an interesting case of phosphoresence in connection | luminosity is of common occurrence, and it would be excepwith the brandling. It was one warm July night in the year tionally valuable to record the period of the year, the state of 1881, when he was exploring a dung-heap. Naturalists do not the atmosphere, the age of the moon, and other data which usually work with kid gloves and diamond rings. Presently a would enable the specialist to arrive at a satisfactory conclusion. spot of soft, bluish-white light appeared, which, however, was I shall be glad to receive communications, addressed “The changeful and unsteady. Now it would disappear, then return Grove, Idie, Bradford," from observers who may find pleasure anew and shine forth over a larger space, though never with a | in such pursuits.
HILDERIC FRIEND. 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
Quaternions and the Algebra of Vectors. without disappearing, or before it migrated to another spot. By IN a recent number of this Journal (p. 151) Mr. means of a lantern Vejdovsky was able to secure a large number of McAulay puts certain questions to Mr. Heaviside and to me, specimens of the brandling from the dung-heap, which he placed relating to a subject of such importance as to justify an answer in a vessel for the purpose of subjecting them to careful obser. somewhat at length. I cannot of course speak for Mr. Heavi. vation. To his great surprise he found that his finger soon side, although I suppose that his views are not very different glowed in the darkness with the phosphorescence, which ex- || from mine on the most essential points, but even if he shall have tended generally over the hand where it came into contact with already replied before this letter can appear, I shall be glad to the worms. It was therefore apparent that the luminosity was add whatever of sorce may belong to independent testimony. the product of a fluid secreted by the cutaneous glands, which Mr. McAulay asks: “What is the first duty of the physical had attached itself to the hand of the investigator, and now | vector analyst quà physical vector analyst?” The answer is manifested itself in this curious way.
not doubtful. It is to present the subject in such a form as to We have an interesting observation on the same subject by | be most easily acquired, and most useful when acquired. Prof. von Stein, which was published at Leipzig in 1883. One 1 In regard to the slow progress of such methods toward recogevening in the middle of September the Professor was spending nition and use by physicists and others, which Mr. McAulay some time with a circle of friends at a parsonage not far from deplores, it does not seem possible to impute it to any want of Potsdam, when the conversation turned upon phosphorescence uniformity of notation. I doubt whether there is any modern and the phenomena of light. Hereupon one of the younger | branch of mathematics which has been presented for so long a members of the family—who are usually the keenest and most time with a greater uniformity of notation than quaternions. shrewd observers of Nature, and the best friends of the naturalist What, then, is the cause of the fact which Mr. McAulay and --observed that there were fountains in the adjoining gardens, all of us deplore? It is not far to seek. We need only a glance the water from which was frequently observed to be full of at the volumes in which Hamilton set forth his method. No light-bearing creatures when it was violently agitated. He re wonder that physicists and others failed to perceive the garded the affair at first simply as a hoax, or an attempt to make possibilities of simplicity, perspicuity, and brevity which a fool of him-as people are ever ready to do with a hobby-rider were contained in a system presented to them in pon--but ascertained eventually that the luminosity was due to the derous volumes of 800 pages. Perhaps Hamilton may presence of a species of worm which possessed the property of have intended these volumes as a sort of thesaurus, and we shining when disturbed. As with Vejdovsky, so with Prof. | should look to his shorter papers for a compact account von Stein, the finger which had come into contact with the of his method. But if we turn to his earlier papers on Quat. worm continued to glow for some time after. What species of | ernions in the Philosophical Magazine, in which principally he worm was under observation is not recorded.
introduced the subject to the notice of his contemporaries, we It now hecomes a question, What end could be served | find them entitled “On Quaternions; or on a New System of thereby? The philosopher no sooner learns a new fact than he Imaginaries in Algebra,” and in them we find a great deal begins to pry into the secret which lies beneath, and stands to about imaginaries, and very little of a vector analysis. To show it as cause to effect. We have analogy to guide us. The water how slowly the system of vector analysis developed itself in the worms may be compared with the marine animals which pro quaternionic nidus, we need only say that the symbols S, V, and duce phosphorescence, while the brandling may be studied in ý do not appear until two or three years after the discovery of the light of the glow-worm. It may be objected that as worms quaternions. In short, it seems to have been only a secondary have no eyes there can be no advantage in their luminosity. object with Hamilton to express the geometrical relations of But such an argument would be based on the erroneous assump vectors, --secondary in time, and also secondary sin this, that it tion that a creature without eyes is incapable of receiving was never allowed to give shape to his work. impressions from light. That worms are influenced by light is But this relates to the past. In regard to the present status, proved both by their habit of avoiding light, and by the experi. I beg leave to quote what Mr. McAulay has said on another ments which have been carried out by various students. Darwin occasion (see Phil. Mag. June, 1892) :-" Quaternions differ remarks that as worms are destitute of eyes he at first thought in an important respect from other branches of mathematics they were quite insensible to light. He found, however, that “light that are studied by mathematicians after they have in the course affects worms by its intensity and by its duration." Hoffmeister of years of hard labour laid the foundation of all their future states that with the exception of a few individuals worms are work. In nearly all cases these branches are very properly so extremely sensitive to light, and from my own observations I called. They each grow out of a definite spot of the main tree have been able to demonstrate that there are marked differences of mathematics, and derive their sustenance from the sap of in the susceptibility of the different species--some being very the trunk as a whole. But not so with quaternions. To let these much more susceptible than others.
grow in the brain of a mathematician, he must start from the Now it follows that if a number of species of worms lived seed as with the rest of his mathematics regarded as a whole. together in one place, as they usually do in a manure heap, it He cannot graft them on his already flourishing tree, for they would be a great advantage for a given species to possess a dis will die there. They are independent plants that require sep. tinguishing feature, such as that of luminosity, to enable two arate sowing and the consequent careful tending." individuals to discover each other's whereabouts, just as the Can we wonder that mathematicians, physicists, astronomers, male glow-worm detects the female by the light emitted from and geometers feel some doubt as to the value or necessity of her upturned abdomen. We have, moreover, the fact that someihing so separate from all other branches of learning? Can certain species of earthworm are characterised by a peculiar that be a natural treatment of the subject which has no relations odour, which must be of great service in preventing promiscuous to any other method, and, as one might suppose from reading copulation and hybridity. Though earthworms are destitute of some treatises, has only occurred to a single man? Or, at best, nasal organs they can detect odours, and though sightless they is it not discouraging to be told that in order to use the quaterare affected by light.
nionic method, one must give up the progress which he has Viewed in this light a new field of research is opened up | already made in the pursuit of his favourite science, and go back which hitherto has been totally unworked, but which may be to the beginning and start anew on a parallel course ? hoped to yield remarkable results if diligently, patiently, and in I believe, however, that if what I have quoted is true of vector telligently tilled.
methods, it is because there is something fundamentally wrong
in the presentation of the subject. Of course, in some sense I should hardly dare to express myself with so much freedom, and to some extent it is and must be true. Whatever is special, if I could not shelter myself behind an authority which will not accidental, and individual, will die, as it should ; but that which | be questioned. is universal and essential should remain as an organic part of I do not see that I have done anything very different from the whole intellectual acquisition. If that which is essential what the eminent mathematician upon whom Hamilton's dies with the accidental, it must be because the accidental hai. mantle has fallen has been doing, it would seem, unconsciously, been given the prominence which belongs to the essential. For Contrast the system of quaternions, which he has described in myself, I should preach no such doctrine to those whom I wish his sketch of Hamilton's life and work in the North Britis to convert to the true faith.
Review for September, 1866, with the system which he urges In Italy, they say, all roads lead to Rome.. In mechanics, upon the attention of physicists in the Philosophical Magazin kinematics, astronomy, physics, all study leads to the considera in 1890. In 1866 we have a great deal about imaginaries, and tion of certain relations and operations. These are the capital nearly as much about the quaternion. In 1890 we have nothir notions ; these should have the leading parts in any analysis about imaginaries, and litile about the quaternion. Prof. Tai suited to the subject.
has spoken of the calculus of quaternions as throwing off in the If I wished to attract the student of any of these sciences to course of years its early Cartesian trammels. I wonder that be an algebra for vectors, I should tell him that the fundamental does not see how well the progress in which he has led may be notions of this algebra were exactly those with which he was described as throwing off the yoke of the quaternion. A daily conversant. I should tell him that a vector algebra is so characteristic example is seen in the use of the symbol y far from being any one man's production that half a century Hamilton applies this to a vector to form a quaternion, Tait to ago several were already working toward an algebra which form a linear vector function. But while breathing a new lif: should be primarily geometrical and not arithmetical, and that into the formula of quaternions, Prof. Tait stands stoatly by the there is a remarkable similarity in the results to which these letter. efforts led (see Proc. A.A.A.S. for 1886, pp. 37, ff.). I should . Now I appreciate and admire the generous loyalty towan! call his attention to the fact that Lagrange and Gauss used the one whom he regards as his master, which has always led Pror, notation (aby) to denote precisely the same as Hamilton by his Tait to minimise the originality of his own work in regard ! Saßy), except that Lagrange limited the expression to unit quaternions, and write as if everything was contained in thvectors, and Gauss to vectors of which the length is the secant ideas which flashed into the mind of Hamilton at the classic of the latitude, and I should show him that we have only to Brougham Bridge. But not to speak of other claims of give up these limitations, and the expression (in connection with historical justice, we owe duties to our scholars as well as to 09: the notion of geometrical addition) is endowed with an immense teachers, and the world is too large, and the current of moden wealth of transformations. I should call his attention to the thought is too broad, to be confined by the ipse dixit even oi a fact that the notation [rr.], universal in the theory of orbits, is | Hamilton.
J. WILLARD GIBbs. identical with Hamilton's V (pipa), except that Hanilton 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
Glacial Drift of the Irish Channel. simple modification (and with the notion of geometrical addi It seems of interest to record that the eurite or microgranite tion of surfaces as well as of lines) this expression becomes containing blue amphibole (Riebeckite), the rock noticed by closely connected with the first-mentioned, and is not only | Mr. P. F. Kendall in the drifts of the Isle of Man and Caernarendowed with a similar capability for transformation, but en vonshire, occurs abundantly in the form of small pebbles on the riches the first with new capabilities. In fact, I should tell him shore at Killiney, co. Dublin, doubtless derived from be that the notions which we use in vector analysis are those which “glacial gravels" of the coast. I have also found a pebble in he who reads between the lines will meet on every page of the the raised beach at Greenore, co. Down. great masters of analysis, or of those who have probed deepest Mr. Teall's description of the rock of Ailsa Craig (MinerI'the secrets of nature, the only difference being that the vector ogical Magasine, vol. ix. p. 219) enabled the very characteristic analyst, having regard to the weakness of the human intellect, pebbles collected by Mr. Kendall to be referred to that mass 3 does as the early painters who wrote beneath their pictures a source, or to formerly existing bosses south of or adjacent to r. “ This is a tree," " This is a horse."
As far as I am aware, all the material is in the form of pebble. I cannot attach quite so much importance as Mr. McAulay to osten only an inch in diameter. This is hardly likely to be it uniformity of notation. That very uniformity, if it existed original condition, if removed by ice from Ailsa Craig, add among those who use a vector analysis, would rather obscure only one of many points that indicate a redistribution of our sc than reveal their connection with the general course of called “glacial" beds by subsequent action of rivers or other modern thought in mathematics and physics. There waters.
GRENVILLE A. J. COLE. are two ways in which we may measure the progress of Royal College of Science for Ireland, Dublin, any reform. The one consists in counting those who have
THE SACRED NILE.
THAT Egypt is the gift of the Nile is a remark we ove is certainly important, and I assure Mr. McAulay that reluctance to make unnecessary innovations in notation has been a
to the father of history, who referred not only to the very powerful motive in restraining me from publication. Indeed
| fertilising influence of the stream, but to the fact that my pamphlet on “Vector Analysis," which has excited the the presence of the Nile and its phenomena are the animadversion of quaternionists, was never formally published, conditions upon which the habitability of Egypt akealthough rather widely distributed, so long as I had copies together depends. That that part of Egyptian archæology distribute, among those who I thought might be interested in and myth which chiefly interests astronomers is also the the subject. I may say, however, since I am called upon to gift of the Nile is equally true. desend my position, that I have found the notations of that The heliacal rising of Sirius and other stars at the time pamphlet more flexible than those generally used. Mr. McAulay, of the commencement of the inundations each year : 2 at least, will understand what I mean by this, if I say that some the myths which grew out of the various symbols of the of the relations which he has thought of sufficient importance to
stars so used, are so many evidences of the large share express by means of special devices (see Proc. R. S. E., for
the river, with its various water levels at different times, 1890-91), may be expressed at least as briefly in the notations which I have used, and without special devices.
had in the national life. It was, in fact, the true and unique
But I should not have been satisfied for the purposes of my pamphlet with
basis of the national life. any notation which should suggest even to the careless reader
In this the Nile had a compeer, or even compeers any connection with the notion of the quaternion. For I con
What the Nile was to Egypt the Euphrates and Tigris fess that one of my objects was to show that a system of vector
| were to a large region of Western Asia, where also *
were to a large region of Western Asia, Wa analysis does not require any support from the notion of the find the annual flood to have been in ancient times a quaternion, or, I may add, of the imaginary in algebra. source of fertility over an enormous area which is 218
desert, the plains being broken by the remains of the Then at last comes the inundation :2 ncient canals.
“ Perhaps there is not in Nature a more exhilarating What more natural than that Euphrates, Tigris and sight, or one more strongly exciting to confidence in God, Nile were looked upon as deities; that the Gods of than the rise of the Nile. Day by day and night by night, its the Nile valley on the one hand, and of the region
turbid tide sweeps onward majestically over the parched watered by the Euphrates and Tigris on the other, sands of the waste, howling wilderness. Almost hourly, were gods to swear by; that they were worshipped
as we slowly ascended it before the Etesian wind, we in order that their benign influences might be secured, heard the thundering fall of some mud-bank, and saw by and that they had their local shrines and special cults. the rush of all animated Nature to the spot, that the Nile
The god sacred to the Euphrates and Tigris was called had overleapt another obstruction, and that its bounding Ea. The god sacred to the Nile was called Hapi.
waters were diffusing life and joy through another desert. The name Hapi is the same as that of the bull There are few impressions I ever received upon the Apis, the worship of which was attributed to Mena.1 | remembrance of which I dwell with more pleasure than Certainly Mena, Mini, or Menes, as he is variously / that of seeing the first burst of the Nile into one of the called, was fully justified in founding the cult of the river | great channels of its annual overflow. All Nature shouts god, for he first among men appears to have had just for joy. The men, the children, the buffaloes, gambol in ideas of irrigation ; and I have heard the distin its refreshing waters, the broad waves sparkle with shoals guished officers who have lately been responsible for | of fish, and fowl of every wing flutter over them in clouds. the irrigation system of to-day speaking with admira
Nor is this jubilee of Nature confined to the higher orders. tion of the ideas and works of Menes.
of creation. The moment the sand becomes moistened Whether the Tigris had a Menes in an equally early
by the approach of the fertilising waters, it is literally time is a point on which history is silent ; but, according to
alive with insects innumerable. It is impossible to stand the accounts of travellers, the Tigris in flood is even more
by the side of one of these noble streams, to see it every majestic than the Nile, and yet the latter river in flood is moment sweeping away some obstruction to its majestic a sight to see a whole fertile plain turned into, as it course, and widening as it flows, without feeling the heart were, an arm of the sea, with here and there an island,
to expand with love and joy and confidence in the which on inspection turns out to be a village, the mud
great Author of this annual miracle of mercy." houses of which too often are underinined by the lapping
The effects of the inundation, as Osburn shows in of the waves in the strong north wind.
another place, “exhibit themselves in a scene of fertility There is no doubt that the dates of the rise of these and beauty such as will scarcely be found in another rivers not only influenced the national life but even the country at any season of the year. The vivid green of religions of the dwellers on their banks. The Euphrates the springing corn, the groves of pomegranate trees and Tigris rise about the time of the spring equinox-the ablaze with the rich scarlet of their blossoms, the fresh religion was equinoxial, the temples were directed to the
breeze laden with the perfumes of gardens of roses and east. The Nile rises at a solstice--the religion was solsti orange thickets, every tree and every shrub covered with cal and the solar temples were directed no longer to the sweet-scented flowers. These are a few of the natural east. To the Egyptians the coming of the river to the
beauties that welcome the stranger to the land of Ham. parched land was as the sunrise chasing the darkness
There is considerable sameness in them, it is true, for he of the night; the sun-god of day conquering the star
would observe little variety in the trees and plants, gods of night; or again the victorious king of the land
whether he first entered Egypt by the gardens of Alexslaughtering his enemies.
andria or the plain of Assouan. Yet is it the same everyBy no one, perhaps, have the impressions produced by
where, only because it would be impossible to make any the various phases of the river been so poetically described
addition to the sweetness of the odours, the brilliancy of as by Osburn, a writer of vivid imagination, but it must be the colours, or the exquisite beauty of the many forms of added that the facts detailed in his description are not ex
| vegetable life, in the midst of which he wanders. It is actly capable of being verified by engineering science.
monotonous, but it is the monotony of Paradise.” Osburn thus describes the low Nile :
“ The flood reaches Cairo on a day closely approxi* The Nile has shrunk within its banks until its
mating to that of the summer solstice. It attains its stream is contracted to half its ordinary dimensions, and greatest height, and begins to decline near the autumnal its turbid, slimy, stagnant waters scarcely seem to flow in
equinox. By the winter solstice the Nile has again subany direction. Broad flats or steep banks of black, sun
sided within its banks and resumed its blue colour. baked Nile mud, form both the shores of the river. All
Seed-time has occurred in this interval. The year in beyond them is sand and sterility ; for the hamseen, or
Egypt divides itself into three seasons-four months of sand-wind of 6fty days' duration, has scarcely yet ceased
sowing and growth, corresponding nearly with our to blow. The trunks and branches of trees may be seen
November, December, January, and February ; four here and there through the dusty, hazy, burning, atmos
months of harvest from March to June ; the four months phere, but so entirely are their leaves coated with dust,
of the inundation completing the cycle." that at a distance they are not distinguishable from the
In order to show how the astronomy of the ancient desert sand that surrounds them. It is only by the most
Egyptians—to deal specially with them—was to a large painful and laborious operation of watering that any tint
extent concerned with the annual flood and all that approximating to greenness can be preserved at this
depended upon that flood, and how the first solar year season even in the pleasure-gardens of the Pacha. The used on this planet, so far as we know, was estat first symptom of the termination of this most terrible
it is important to study the actual facts of the rise someseason is the rising of the north wind (the Etesian wind what closely, not only for Egypt generally, but for several of the Greeks), blowing briskly, often fiercely during the
points in the line some thousand miles in extent, along whole of the day. The foliage of the groves that cover
which in the earliest times cities and shrines were Lower Egypt is soon disencumbered by it of the dust, and
dotted here and there. resumes its verdure. The fierce fervours of the sun, then
Time out of mind the fluctuations in the height of the at his highest ascension, are also most seasonably miti
river have been carefully recorded at different points gated by the same powerful agency, which prevails for
along the river. In the “ Description de l’Egypt” we this and the three following months throughout the entire
find a full description of the so-called nilometer at Assuan land of Egypt."
(First Cataract) which dates from a remote period,
perhaps as early as the 5th Dynasty. Maspero, ". Hist. Anc." xi. 10
In Ebers' delightful book on Egypt space is given to
the description of the much more modern one located at had to hold back many basins in the Gizah province Rodah.
and also in 1888, when the water remained long stagnan, The nilometer, or “mikyas," on the island of Rodah that the basin-water got green-showed the alga an now visible, is stated to have replaced one which was smelt marshy, just as the June green water does. brought thither from Memphis at some unrecorded date. Hence it has been argued that as the Nile-water in the Makreezee in 1417, according to Ebers, saw the remains bed of the stream-even in very slow-flowing back-waters of the older nilometer.
-does not become green, the greenness must be proThe present mikyas is within a covered vault or duced by an almost absolute stagnation of the water. We chamber, the roof being supported on simple wooden know of great marshes up above Gondokoro, and hench pillars. In a quadrangular tank communicating with the it is thought that the green water of summer, which comiei river by a canal is an octagon pillar on which the Arabic on suddenly, is this marsh-water being pushed out by the measurements are inscribed. These consist of the pic new water from behind, and that is why it heralds the (variously called ell or cubit) = 0'54 metre, which is i rise. No one has so far minutely observed the gradau divided into twenty-four kirats, in consequence of the intrusion of the green water. rise of the river bed in relatively recent times, the nilo The rise of the river proceeds rapidly, and the water meter is submerged at high Nile to a depth of two gradually becomes more turbid. Ten or twelve days. cubits.
however, elapse before the development of the last and The rise of the Nile can now be carefully studied, as most extraordinary of all the appearances of the Nik, gauges are distributed along the river. We have the thus described by Mr. Osborn? “ It was at the end & Aswân gauge from 1869, the Armant gauge from 1887, -to my own sensations-a long and very sultry night the Suhag gauge from 1889, and the Asyllt gauge from that I raised myself from the sofa upon which I had it 1882. The distances of these gauges from Aswân are as vain been endeavouring to sleep, on the deck of a Nike follows:
boat that lay becalmed off Benisoueff, a town of Middle Kilometres
"The sun was just showing the upper limb of his dis Armant
over the eastern mountains. I was surprised to see that 447
when his rays fell upon the water, a deep ruddy reflectio
550 Rodah ...
was given back. The depth of the tint increased cot:
tinually as a larger portion of his light fell upon the The Rodah gauge is not to be depended on as the water, and before he had entirely cleared the top of the movements of the Barrage regulation destroy its value hill it presented the perfect appearance or a river of as a record. The heights of the zeros of these gauges blood. Suspecting some delusion, I rose up hastily, x above mean sea level are as follows :
looking over the side of the boat saw there the confirma Metres.
tion of my first impression. The entire body of the water Aswân
was opaque and of a deep red colour, bearing a close Armant ... ... ...
resemblance to blood than to any other natural preSuhag
duction to which it could be compared. I now perceiver Asyllt
that during the night the river had visibly risen seves 13'14
inches. While I was gazing at this great sight, the Aras Great vagueness arises in there being no very obvious came round me to explain that it was the Red Nile. Tk distinction between the gauge readings reached in sum- | redness and opacity of the water, in this extraordinat mer and that from which the rise is continuous. There condition of the river, are subject to constant variatioss are apparently rainfalls in the end of spring of sufficient
end of spring of sufficient | On some days, when the rise of the river has not exceeded power to raise the Nile visibly in summer, just as muddy an inch or two, its waters return to a state of semi-trans rises have been seen in winter to pass down the valley, parency, though during the entire period of the bę leaving a muddy mark on the rocks at Aswân and Nile they never lose the deep red tinge which cannot * Manfalût. Independently of the actual gauge-read-] separated from them. It is not, however, like the green ing of the rise, there are facts about it which strike admixture, at all deleterious; the Nile water is nere every beholder. At the commencement of the rise we more wholesome or more deliciously refreshing than a have the green water. This occurs in June, but varies ing the overflow. There are other days when the rise of 1 in date as much as the top of the flood varies.
river is much more rapid, and then the quantity of me From the fact that modern observations show that the that is suspended in the water exceeds, in Upper LT very beginning of the rise, and the first flush, second flush, that which I have seen in any other river. On more tha and final retirement vary, it seems evident that the ancient | one occasion I could perceive that it visibly interters Egyptians could not have had any fixed zero-gauge or with the flow of the stream. A glassful of it in this star time for the real physical fact of the rise, but must have was allowed to remain still for a short time. The upper either deduced from a series of observations a mean portion of it was perfectly opaque and the colour of batu period of commencement, or a mean arrival of the red ) A sediment of black mud occupied about one quarters water, or a mean rising up to a certain gauge.
the glass. A considerable portion of this is deposit First to deal with the green water. Generally when before the river reaches Middle and Lower Egypt ! the rise of an inch or two is reported from the nilometer never observed the Nile water in this condition there, as .at Rodah, the waters lose the little of clearness and fresh indeed no consecutive observations exist of the redden, ness they still possessed. The green colour is the lustre- of the water. It is quite clear that the reddening can less hue of brackish water within the tropics, and only come from the White Nile, but must be the first floous the finer class of modern filter can render such water the Blue Nile and the Atbara coming down.".. clear. The colour is really due to alga.
Rate of Rise of the Nile.-The rate in flood is 11 de Happily, the continuance of this state of the water from Wady Halfa to Aswân and six days from Aswat seldom exceeds three or four days. The sufferings of Rodah (941 kilometres). In very high Niles this is those who are compelled to drink it in this state, from haps accelerated to five days. In the early flood Tis vesicary disease, even in this short interval, are very | from, say, one cubit Aswân to six cubits, where there a severe. The inhabitants of the cities generally provide many dry sandbanks, and the spreading out of the against it by Nile-water stored in reservoirs and tanks. is considerable, and there is an absence of overlapp
Col. Ross, R.E., noticed in 1887 and in 1890, when, owing to the slow retreat of the Nile, the irrigation officers
I'Monumental Egypt," chapter i.