remarkable African affinity' in the Lepidoptera of Australia, in reference to the case of the larva of Doratophora vulnerans Lewin. The instances which he cites as analogous, however, are very different in character, for he quotes the mention by Livingstone of a caterpillar called Rigura, producing fearful agony if a sore is touched with its entrails'; and the statement made by Baynes and other travellers, that a caterpillar is used by the Bushmen to poison their arrows. It is evident that, if a caterpillar be used at all for poisoning arrows (concerning which report my inquiries have hitherto been attended by no satisfactory result) it must be the intestines or juices of the animal which are so employed. But the case of Doratifera vulnerans is the common one of (what appears to be mechanical) irritation, by means of clusters of spines, a defence possessed by many caterpillars, not only in Australia and South Africa, but throughout the globe, and of which the larva of the European Cnethocampa processionea presents a familiar example. Duncan (Nat. Libr. Ent. vol. vii. Exotic Moths, pp. 181-2. pl. xxii. f. 5) represents the larva of D. vulnerans as possessing four fascicles of rufous spines, exsertile at will on both the anterior and posterior portions of the body, and quotes Lewin to the effect that the wound inflicted by the fascicles is very painful. According to Mr. Murray's account it would appear that the African larvæ, from the handling of which Dr. Welwitsch experienced such suffering, were near allies (if not actually species of Doratifera); and the conclusion is obvious that it was by fascicles of spines that the pain was occasioned-not an uncommon case in the warmer parts of the world, and one by no means indicative of any special relation between the Lepidopterous

faunas of South Africa and Australia."

Mr. Trimen is obviously right as to the absence of analogy between the venomous properties of the caterpillars spoken of by Livingstone and Baynes, and those met with by Dr. Welwitsch, and it was a slip on my part to collocate them together; but I am not satisfied that he is equally right in referring the pain caused by the species of Doratophora to mechanical irritation. He gives no facts in support of his assumption to that effect, and the facts communicated to me by Dr. Welwitsch regarding the insect from which he suffered seem to me wholly inconsistent with that supposition. It may be supposed from his and my silence that we acquiesed in Mr. Trimen's views. But it is not so. When Mr. Trimen's paper appeared Dr. Welwitsch spoke to me upon the point, and I urged him to communicate to the scientific world fuller details of the incident than I had given, and I understood that he intended to do so in any account of the insects collected by him. I therefore did not feel warranted in speaking, which I now regret, for as with much else that he had on hand to do, his life has been too short for him to do it himself. Now that he has passed away from us I should not like an erroneous impression to exist as to the facts; and although I have little to add to what I formerly stated as communicated by him to me, I should wish to repeat it more precisely, and to say that Dr. Welwitsch himself was firmly convinced that it was not a case of mechanical irritation but of a special virus of unusual potency.

In the first place, then, Dr. Welwitsch had heard of this noxious caterpillar before he met with it-the natives knew it well and dreaded it. In the next place when he did meet with it his native attendant warned him of itand they took every precaution against touching it; they plucked leaves on which the caterpillars were feeding and guided them from the leaf into the wide-mouthed bottle or vessel he had to carry such specimens home in. They also took specimens of the plant on which they were feeding. I suggested to him that the sting might have been in the plant, but this he was positive was not the case. The virulence of the venom was such that by the time they reached home in an hour or so after, every tender

part of their body which they had touched with their fingers had become swollen and inflamed; their eyes were closed up, their lips and cheeks swollen as if they had been assisting (as principals) at a prize fight, and the consequent fever was so great that they were laid up, unable to move for two or three days; and when they did get up he found that their attendants had bundled out of the house both the caterpillars and the plants on which they fed. Now it seems to me that mechanical irritation is a wholly inadequate cause for such extreme inflammatory action. Mechanical irritation may go a certain length, but there are bounds beyond which we must look for some other explanation.

But first we want more facts and more examples. I exhibit two caterpillars, apparently different species, which I have received from Old Calabar, given to me with a notandum as reckoned injurious if not venomous, but my information as to them is too vague to allow me to cite them as positive examples of venomous caterpillars. And I also show one from Brazil which I have received from my friend, Mr. Fry, which he informs me bears a very bad character in Brazil. Both of these, indeed, all to which this property has been ascribed, are hairy caterpillars; but then it is only hairy caterpillars that seem to have the necessary apparatus for stinging-all stinging plants, so far as I know, are hairy. If the caterpillars have a special venom, then, as in the nettle, there should be a gland at the base of each hair, which should be hollow, and the spines in most, if not all, our caterpillars are hollow. I know of no physiological reason against their being so made. In the skin of the newt there are pores which exude an acrid irritating fluid. If a hollow hair were placed over the pore with proper muscles, we should then have a parallel to the supposed case.

But, as I said before, we want information as to the existence and amount of this venomous property, and the chief object of this paper to-night is, after eliciting the views of the meeting, to suggest to those who may have the opportunity, the desirableness of making observations on the point.

A. MURRAY

Descartes (Principia pars. 2, "Quid sit spatium, sive locus internus") remarks, "For, in truth, the same extension in length, breadth, and depth, which constitutes space, constituted body; and the difference between them consists only in this: that in body we consider extension as particular, and conceive it to change with the body; whereas in space we attribute to extension a generic unity (genericam unitatem), thus after taking from a certain space the body which occupied it, we do not suppose that we have at the same time removed the extension of the space, because it appears to us that the same extension remains there so long as it is of the same magnitude and figure, and preserves the same situation in respect to certain bodies around it, by means of which we determine the space."

Gauss used to say that one of the happinesses of his future life would be the amplification of his conceptions of space; the realisation of that which he had once known as space of three dimensions, as space of four dimensions. For just as we can conceive of beings "like infinitely attenuated book-worms in an infinitely thin

sheet of paper," which can realise space of only two dimensions, so also we may conceive of beings capable of realising space of four dimensions. Prof. Sylvester, Dr. Salmon, Prof. Clifford, and others, have indicated in some of their profoundest mathematical demonstrations that they possess "an inner assurance of the reality of transcendental space." We desire now to bring forward, with great apology to the mathematicians for our temerity, some ideas, which we believe may enable even the least mathematical amongst us, to realise,-faintly, indeed, and very dimly-the possibility of existence of space, other than that which we now occupy. This we propose to do, (a) by attempting to realise à condition of life in space of two dimensions, and (8) by adding the element of diverse motions, to our already known space.

Our knowledge of the Universe involves the conception of space, time, and number. These are intuitive notions: we cannot strictly define them; in the abstract our notion of them is merely relative; apart from material existence we cannot realise them. Extension is an essential property of matter, and our conception of space is linked with our conception of extension. Robert Hooke, in a series of lectures De Potentia Restitutiva, written nearly two hundred years ago, and too little known, defines a sensible body as "a determinate space, or extension, defended from being penetrated by another, by a power from within." Now this power may be most readily conceived to be a vibratory motion of the particles across a position of rest. Let us imagine an infinitely thin plane vibrating between two fixed points with such velocity that no other matter can penetrate into the space limiting the vibration, then a solid bounded in one direction by the two fixed points would be the result. For example, let an infinitely thin sheet of iron a metre square vibrate with extreme velocity in a span of one metre, and a cubic metre of iron would be the result. The rapid vibration of the plate would defend the range of vibration from being penetrated, and impenetrable material substance would result. An infinitely thin line vibrating between two fixed points would furnish a plane. An infinitely thin plane vibrating between two fixed points would furnish a solid. Thus by the addition of motion we can convert a determinate space, approximately of one dimension, into space of two dimensions; and by the addition of motion we can convert space of two dimensions into space of three dimensions. Can we conceive of any motion which given to space of three dimensions shall generate space of four dimensions? We do not know of such motion, but we can surely conceive the possibility of its existence. Space of four dimensions is transcendental space: it is beyond the limit of our experience, but not beyond the limit of our imagination.

Let us now endeavour to realise the condition of a being living in space of two dimensions. If man possessed the eyes and the power of flight of an eagle, superadded to his ordinary intellectual qualities, he would, no doubt, have very enlarged views of space. As it is, man is distinguished from the brute animals by his erect bearing, and the range of space which his vision enables him to scan. Our eyes are easily movable in various directions, so also is our head; by a slight movement of the head and eyes, we may take in either space bounded by the horizon, or by a surface a foot square. If we throw our head back we enlarge our view of space; if we bend our head forward we narrow our view of space. Now, imagine that a man thus endowed, and with our own notions of space of three dimensions, begins to stoop forward and to grow so: his eyes survey less space; he stoops more forward; his body forms angles of 80°, 70°, 60°, 50° in succession, with a horizontal plane. Then he is obliged to go on all-fours, his limbs shorten and are gradually absorbed into the mass of his body; he crawls, he creeps; at length his limbs disappear altogether, and he trails himself along and glides like a serpent, moving in a hori

zontal plane. During these successive shrinkings in the direction of his thickness his head has become fixed, his eyes motionless, in the plane in which he moves, and his vision has hence become more and more limited. Now his body begins to diminish in thickness; he becomes thinner, and thinner, and thinner, and when he has become very thin indeed, let his thickness be expressed as the numerator of a fraction, while the denominator is an infinitely great number-say, if you will, as many figures as, written on paper, would reach ten billion miles, with ten figures to an inch. Now he is a mere plane, an infinitely thin surface; he occupies space approximately of two dimensions; his eyes are on a line. Try to imagine what the ideas of space of such a being would be; compared with our own ideas of space, compared with his own ideas before and during his process of flattening. He would now contemplate only a plane surface; he would see length and breadth without thickness. Compare also his ideas of space at each and every position between verticality and horizontality as his ken gets less and less, and at last the whole world is shut out from him.

Again, to come nearer home, and back again to the world of real existences, let us compare our own ideas of space after concentrating our vision for awhile on a book a foot square, with our ideas of space acquired while we ascend a lofty mountain, or lie upon our back on the deck of a vessel in mid-ocean. Compare the views of space possessed by a prisoner immured for forty years in a dungeon eight feet square, of La Sachette in the Trou aux Rats, of a being bed-ridden for half a century, with those of a hunter in the prairies of the West, a sailor of the Atlantic, even of a dweller in a flat tame country. The conceptions of space possessed by these different people will vary enormously. Contract the limits of space of possible contemplation; remove the possibility of contemplating space of great dimensions, and the faculty of such contemplation will itself die out; and thus, by a gradual process of diminution, we may arrive at our ideal being, living in space of two dimensions. Finally, let us imagine the being of two dimensions-length and breadth-to become narrower and narrower, and when he has become extremely narrow let us divide his breadth by an infinitely large number, and he becomes approximately of one dimension; he has now only length; he lives in a line; his one motionless eye is a point.

So much for space of less dimensions than our own. Let us now try to conceive an extension of our ordinary space; and let us attempt this by the superaddition of motion to known space. And let us clearly realise the fact that one and the same thing may easily possess various motions at the same time. For instance, when I walk across the room, talking the while; my vocal chords possess five distinct motions: (a) their own proper motion of vibration; plus (B) the motion of translation caused by walking forward; plus (y) the motion of rotation of the earth about its axis; plus (8) the motion of revolution of the earth about the sun; plus (e) the motion of translation of the whole solar system through space. Let us suppose now that our bodies, instead of being at apparent rest, were to vibrate in arcs, with an amplitude of 10,000 miles, and with an infinite velocity; and let the plane of the direction of vibration itself vibrate between limits 10,000 miles apart; and let the whole vibrating system move with infinite velocity in a circle 1,000,000 miles diameter; and let the circle rotate upon its diameter; and let the sphere of revolution thus formed revolve in an infinitely great ellipse; and let the ellipse rotate upon one of its axes; andbut hold! we have surely arrived at a somewhat enlarged view of our own relations to space. Conceptions of this nature sufficiently pursued may, perchance, lead us to the very threshold of transcendental space; and, once on the threshold, we may look wonderingly beyond. G. F. RODWELL

I

ON THE SPECTROSCOPE AND ITS APPLICATIONS

VIII.

TOLD you I had something more to say about the spectrum of blood, and this is not only an instance of the way in which the spectrum helps us in several important questions that, at first sight, do not seem at all connected with each other, but it shows the enormous power of research that is open to us. The colouring matter of blood, for instance, is found, like that of indigo, to exist in two perfectly different states, which give two perfectly different spectra. The colouring matter of blood is indeed capable of existing in two states of oxidation, which are distinguishable by a difference in colour, and also in their action on the spectrum. They may be made to pass one into the other by suitable oxidising and reducing agents; they have been named by Professor Stokes, their discoverer, red and purple cruorine. Previous to the introduction of spectrum analysis, red and purple cruorine were perfectly unknown. Further, if by means of a spectrum microscope, such as I have already described, a blood-stain is examined, Mr. Sorby asserts that the thousandth part of a grain of blood, -that is to say, a blood-spot so small that it only contains 1000 of a grain, is perfectly easy of detection by means of this new method, and he has shown that its presence may be easily proved in stains that have been kept for a long time, and recognised even after a period of fifty years.

1

a paper in which he narrates the result of his inquiries on the yellow organic substances contained in animals and plants; and at the present moment it is impossible to say what important practical results may be expected as we come to know more about these substances, especially in the matter of dyes, which I am sure is a thing that will commend itself to you.

Again, Mr. Sorby, in a communication to the Microscopical Society, brings the matter still nearer home. He shows us that, in the case of wines, he can, by means of the absorption bands, determine the very year even of vintage, and this, you will see at once, is a matter of very great importance. Let me read you an extract from one of Mr. Sorby's reports. He says:-"The difference for each year is at first so considerable that wines of different vintages could easily be distinguished; but after about six years, the difference is so small that it would be difficult or impossible to determine the age to within a single year. After twenty years, a difference of even ten years

He has also shown how it may be detected under the most unfavourable conditions, provided that a trace of hæmatin has escaped decomposition or removal; he has, in fact, successfully applied this method in several important criminal cases.

Another very interesting fact is, that when blood contains very small quantities of carbonic oxide gas in solution, it exhibits a very curious series of absorption bands. This fact is of considerable value in toxicological research, for in cases of poisoning by the so-called charcoal fumes, where, as is well known, the poisonous action is due to the formation of carbonic oxide, it can be readily detected by the peculiar bands which the blood under these cir

cumstances exhibits.

Mr. Sorby has also applied the spectrum microscope to the study of blow-pipe beads, and has shown that in some cases as small a quantity as 10000th of a grain of some substances can be thus recognised, even when mixed with other coloured bodies, which would interfere with the usual reactions dependent on colour alone.

In the case of radiation, as you know, we are able to determine the existence of new elements altogether. This is produced to a certain extent, as in the above case, in the absorption spectrum. Let me give you another prac tical application of this principle. Dr. Thudichum, as a result of researches made for the Medical Department of the Privy Council, has communicated to the Royal Society

FIG. 48.--Coincidence between the right line given out by sodium vapour and the dark line produced by the absorption of sodium vapour.

could

does not show any striking contrast, and the age not, therefore, be determined to nearer than ten years by this process. However, up to six years I think it quite possible to determine the age to within a single year. I took specimens of various ports from the casks, of different manner that I did not know the age of any, but could ages up to six or seven years, and labelled them in such a ascertain it afterwards by reference. I then made the experiments with great care, and found that, by proper attention to the details described above, I could correctly determine the year of vintage of each particular specimen." (Chemical News, December 17, 1869, p. 295.)

We have, in fact, a definite method of analysis of animal and vegetable colouring matter, and also of the colouring matter of decayed wood. Nor is this all, for, in another communication-for these things are now beginning to crowd upon us, and they will continue to do so much more by-and-by-Dr. Phipson asserts that this new method is perfectly competent to indicate any ari

the light has passed. If sodium vapour be traversed, then the light corresponding to the bright lines of sodium will be enfeebled.

This great law, to which the researches of Stokes and

Stewart and Angström have led, and which has been established by the experiments of Foucault, Kirchhoff, and Bunsen, may be summed up as follows :-Gases and vapours, when relatively cool, absorb those rays which they themselves emit when incandescent; the absorption is continuous or selective as the radiation is continuous or selective. J. NORMAN LOCKYER

(To be continued.)

NOTES

THE Emperor of Brazil has conferred upon Dr. Warren De La Rue the distinction of Knight of the Imperial Order of the Rose.

THE subject of Professor Tait's Rede Lecture, to be delivered on the 23rd inst., will be "Thermo-Electricity."

A PARAGRAPH has recently appeared in several scientific papers quoted from the Zeitschrift für Parasitenkunde, stating that Prof. Hallier of Jena has described a new potato-disease, which made its appearance last autumn in the neighbourhood of that town, the disease being indicated by the presence of a purple web and the appearance of a number of black spots on the skin, referable apparently to the perithecia of a pyrenomycetous fungus. We learn from the Rev. M. J. Berkeley that this so-called new disease is nothing but the well-known " copper-web" which is in some years very destructive to asparagus, mint, and other crops, and has been known in some instances to attack the potato. The description in the Zeitschrift is identical with this familiar parasite. Figures will be found in Tulasne's "Fungi Hypogai," under Rhizoctonia, showing that the so-called perithecia are spurious. Mr. Broome has detected the form of fructification known as conidia.

LADY LYELL, wife of Sir Charles Lyell, Bart, F.R.S., died last Thursday, in her 65th year. Her ladyship was the eldest daughter of the late Mr. Leonard Horner, F. R.S.

DURING the Easter term the following lectures in natural sciences will be given at Cambridge :-On Heat (1) Advanced (for the Natural Sciences Tripos), by Mr. Trotter, Trinity College, in Lecture-room No. II, on Mondays, Wednesdays, and Fridays at 10, commencing Wednesday, April 30 (2) Elementary (for Special Examination and 1st Part of Natural Sciences Tripos), on Tuesdays, Thursdays, and Saturdays at 11, commencing Tuesday, April 29. On Chemistry, by Mr. Main, St. John's College, on Tuesdays, Thursdays, and Saturdays at 12, in St. John's College Laboratory, commencing Thursday, April

24.

Instruction in Practical Chemistry will also be given. On Paleontology-the Mollusca, &c., by Mr. Bonney, St. John's College, on Tuesdays and Thursdays, at 9, commencing Thursday, April 24. On Geology-(for the Natural Sciences Tripos, Stratigraphical Geology), by Mr. Bonney, St. John's College, on Mondays, Wednesdays, and Fridays, at 10, commencing Wednesday, April 23. Elementary Geology (for the First part of the Tripos and the special examination), on Tuesdays and Thursdays, at II, commencing Thursday, April 24; there will be excursions, of which notice will be given from time to time. On Botany (for the Natural Sciences Tripos), by Mr. Hicks, Sidney College, on Tuesdays, Thursdays, and Saturdays, at II, in Lecture-room No. 1, beginning on Tuesday, April 29; the lectures during this term will be chiefly on Cryptogamic Botany and on Classification. Biology: the Trinity Prælector will give a course of Practical Lectures on Elementary Biology, on Mondays, Tuesdays, and Wednesdays, at II A. M., commenc

ing Wednesday, April 30. This course is intended as an introduction to the study of both anatomy and physiology. A short lecture of about half-an-hour will be given at each meeting, fol

lowed by practical work for about 1 or 2 hours.

THE annual soirée of the Royal Society last Saturday at Burlington House was a great success. The number of visitors was exceedingly large, and the objects exhibited were numerous and varied. In the Mathematical Room, Mr. Latimer Clark showed his remarkable experiment of the influence of light on the conductivity of selenium, recently described in NATURE,

THE office of "Lord Rector" of a Scotch University is generally regarded as merely honorary, a testimony of the estimation in which the students hold the gentleman whom they elect. As a rule the Lord Rector acquiesces in this opinion, and seldom does more in return for the supposed honour conferred than mark the commencement or close of his three years' tenure of office by making a speech to the students. As might be surmised, Prof. Huxley, who was recently elected to the Lord Rectorship of Aberdeen University, which counts Prof. Bain among its staff of teachers, does not regard the office as merely honorary: he intends to take advantage of the position conferrred upon him by doing some actual work for the good of the University. Naturally one of the first grievances he has attacked is the medical curriculum, which at Aberdeen, as at most other medical schools, is hampered by the "traditions of the elders" as to the supposed advantages of the dead languages to a medical s'udent. Shortly after Prof. Huxley's election, he received a numerously signed petition from the medical students requesting him to use his influence to obtain the omisssion of Greek as a compulsory subject in the preliminary examination. Prof. Huxley has given notice that he will bring forward at the next meeting of the University Court a resolution to reform the medical curriculum at Aberdeen, as he considers it at present rather overweighted with classics, and believes that some new arrangement would probably be exceedingly advantageous, especially in the matters of natural history and botany.

WE hear from Mr. Lloyd that living specimens of the Lancelet (Amphioxus lanceolatus) have been very recently received at the Crystal Palace Aquarium, from Naples, and are now alive. We hope that Dr. Dohrn will be successful in sending other living specimens of this most interesting fish to other Aquaria in this country, so that its affinities and development may be more thoroughly worked out and generally understood.

MR. THOMAS WILLIAM BRIDGE was on Friday elected to a Natural Science Scholarship at Trinity College, Cambridge. Mr. Bridge has for some two years worked under Mr. J. W. Clark, the Superintendent of the University Museums of Zoology and Comparative Anatomy, and about a month since was appointed, by the Professor of Zoology, to the newly-founded post of Demonstrator in Comparative Anatomy in the University.

DR. DIVERS, of the Middlesex Hospital, has been appointed to the Professorship of Chemistry in the new Engineering College at Jeddo.

PROF. AGASSIZ has not been behindhand in employing the advantages placed at his disposal by Mr. Anderson's munificent bequest. A programme is already published of a summer course of Natural History at Penekese Island, designed chiefly for teachers, and for students preparing to become teachers. Among those that Prof. Agassiz is able to include on his staff we find the names of Profs. Shaler, Wilder, Packard, and Putnam, and every attempt is being made to obtain a sufficient endowment, through the liberality of others, to offer the course free of charge to deserving students. The Superintendent of the United States Coast Survey and the United States Commissioner of Fisheries have also promised all the assistance in their power to this excellent undertaking.