pied by the reversing layer, which is tion-coil, all the beautiful flutings in the competent, as we know from other consid-carbon spectrum disappear utterly; that erations, to drive even carbon and silicon into the extremest stage of dissociation, supposing carbon and silicon to be there. The train of reasoning which enables us to suggest that such a temperature must exist in such and such a region of the solar atmosphere, depends, in the main, upon questions raised by the differences between the spectra of certain bodies in the sun and in our laboratories. If, for instance, one wishes to observe the coincidence between, let us say, iron and the sun, iron is placed in the electric lamp; the spectrum of the light of its vapor is photographed; above this spectrum on the same plate the spectrum of the sun is also photographed; and as a rule (I say as a rule, but this is not absolute even in the case of such metals as iron), the intensity of the iron-lines which we get from the iron vapor in our laboratories is equivalented by the intensity of the so-called iron-lines which we assume we observe in the spectrum of the sun. That is the great argument, in fact, for the existence of iron in the sun. kind of carbon is no longer present in the reaction; instead of them we have a kind of carbon which is only competent to give us bright lines; and we know that those bright lines do not exist reversed in the spectrum of the sun, though the channelled spaces do. Hence we assume the carbon to lie in a cooler and therefore higher region. In what I have written up to this point (and I have just touched slightly on the physical side of the work, because I believe that in the future it will be most rich in teachings of the kind I have indicated), I have dealt solely with the Fraunhofer that is the dark lines in the solar spectrum. Now it is knowledge ten years old, that if we observe the solar spectrum with that considerable dispersion which is now imperative if we are to do much good with it, there are bright lines in the ordinary solar spectrum side by side with the dark ones. In a paper communicated to the Royal Society in 1868, attention was drawn to But when we leave the iron group of these bright regions in the ordinary specmetals, we find others in which this co-trum, and the position of certain bright incidence, this great similarity of intensity lines was stated. These bright lines have from one end of the spectrum to the since been rediscovered both by Henother, is considerably changed. We get nessy and Cornu. I will here call espein the case of calcium very thick lines cial attention to one line, because the corresponding with very thin lines in the requisite amount of dispersion is now so sun, and we get thin lines of calcium cor- generally available, that any one, whenresponding with very thick lines in the ever the sun shines, may turn to b, the sun. In fact, the two thickest lines which triple dark line in the green part of the have already been mapped in the spectrum spectrum, and see that bright line for of the sun are lines due to calcium. If we himself. It will be found just as much photograph the spectrum of calcium with a outside the fourth line of b as the third is very weak arc in an electric lamp the lines on the other side of it. This bright line, most obvious in the spectrum of the sun lying in the most visible part of the specwould scarcely be visible at all on the trum, is exactly similar to many others, photographic plate. If, however, we pass some of them in the yellow and some of from the tension of the arc to the tension them in the red. A careful list of these which is obtainable with the use of a very lines was made by myself some years ago; large coil, then we can exactly equivalent and, I am sorry to say, the list was unthe spectrum which we get artificially with fortunately left in a Metropolitan Railway the spectrum with which the sun presents carriage by one of my assistants; at all us naturally; and the more we increase events, enough was said in this and other the tension the larger the coil, and the countries about these bright lines in the larger the jar we employ up to a certain years 1869 and 1870 to have given rise, at point the more can we make our terres-all events, to the hope that any one intertrial calcium vibrate in harmony, so to speak, with the calcium which exists in the atmosphere of the sun. This gives us some very precious knowledge. We know that to get things into harmony, as I said before, we must employ a large induction-coil; and we know, again, that if we do employ a large induc ested in solar physics would be perfectly familiar with them. Among other matters which called attention to the fact of their existence was a correspondence which took place in the Comptes Rendus of the Academy of Sciences in Paris between Father Secchi and another observer in connection with solar spots. I have insisted upon the fact that a large dispersion is requisite to see these bright lines, because with a small dispersion bright regions of the sun are very apparent. These, however, are due to the absence of fine lines; and, indeed, if one observes the solar spectrum with considerable dispersion through a cloud which prevents the fine lines being seen, then there is a very considerable diminution in the intensity of some parts of the spectrum, and a considerable relative increase in others, where these very fine lines are present and absent respectively. When, however, considerable dispersion is employed and photography is brought into play, if precautions be taken to give sufficient exposure, these bright regions, as opposed to the bright lines, entirely dis appear. During the course of last year Dr. Draper, of New York, published the first results of a research which he has undertaken, going over very much the same ground with regard to the metalloids as had been gone over in this country with regard to the metals. Dr. Draper, who has long been known as an earnest student of science, approached this subject with a wealth of instrumental means almost beyond precedent; and his well-known skill and assiduity enabled him to accumulate facts of the very greatest importance in the course of the two or three years during which his work was carried on. I am most anxious to make these preliminary remarks, and to state my very highest respect for Dr. Draper, because in going over his work I find that some of his results are, in my opinion, open to doubt. Dr. Draper, in the first instance, apparently unaware of what has hitherto been published with regard to them, announces the discovery of the bright lines already referred to, and more than this, he bases a new theory of the solar constitution upon them. It is by no means as a stickler for priority that I regard this as a very great pity; but because I think that if the very considerable literature touching these bright lines the papers by Young, Cornu, Hennessy, Secchi, and others - had been before Dr. Draper when his memoir was written, the necessity for the establishment of a new theory of the solar spectrum, which doubtless cost him very considerable thought, would probably have been less obvious. As a matter of fact, one of the first lines recorded in the spectrum of the chromosphere in 1868 raised the whole question, because there was no dark Fraunhofer line corresponding 379 with it in the ordinary spectrum of the sun. Before I proceed further it will be best to give some extracts from Dr. Draper's memoir. He writes: in the solar spectrum, and does not give dark Oxygen discloses itself by bright lines or bands aborption lines like the metals. We must therefore change our theory of the solar spectrum, and no longer regard it merely as a continuous spectrum with certain rays absorbed by a layer of ignited metallic vapors, but as having also bright lines and bands superposed on the background of continuous spectrum. Such a conception not only opens the way to the discovery of others of the nonrine, bromine, iodine, fluorine, carbon, etc., metals, sulphur, phosphorus, selenium, chlo. but also may account for some of the so-called dark lines, by regarding them as intervals between bright lines. It must be distinctly understood that in speaking of the solar spectrum here, I do not mean the spectrum of any limited area upon the disc or margin of the sun, but the spectrum of light from the whole disc. I have not used an image of the sun upon the slit of the spectroscope, but have mirror of the heliostat without any condenser. employed the beam reflected from the flat The photograph of the solar spectrum which accompanies Dr. Draper's paper contains a spectrum of the sun compared with that of air and also some of the lines of iron and aluminium. The photograph itself is absolutely free from handwork or retouching. It is, as Dr. Draper points out, difficult to bring out in a single photograph the best points of these various subtances. conditions which conspire for the production There are so many variables among the of a spectrum that many photographs must be taken to exhaust the best combinations. The pressure of the gas, the strength of the original current, the number of Leyden jars, the separation and nature of the terminals, the number of sparks per minute, and the duration of the interruption in each spark, are examples of these variables. Still, in the particular photograph placed in evidence, Dr. Draper is of opinion that No close observation is needed to demonstrate to even the most casual observer that the oxygen lines are found in the sun as bright lines, while the iron lines have dark representatives. And he gives a list of many such coincidences. In order to be certain that a line belongs to oxygen, Dr. Draper has compared, under various pressures, the spectra of air, oxygen, nitrogen, carbonic acid, car buretted hydrogen, hydrogen, and cyano- | bright bands near G, from wave-lengths 4307 gen. Where these gases were in Plücker's tubes a double series of photographs has been needed, one set taken with and the other without Leyden jars. To account for this wonderful discovery coming so late, it is urged that to 4337, which are only partly accounted for by oxygen. Farther investigation in the direction I have thus far pursued will lead to the discovery of other elements in the sun, but it such researches are to be conducted for the is not proper to conceal the principle on which sake of personal advantage. It is also probthe enigma of the D3 or Helium line, and the able that this research may furnish the key to 1474 K or Corona line. The case of the D3 The bright lines of oxygen in the spectrum of the solar disc have not been hitherto perceived, probably from the fact that in eye-line strengthens the argument in favor of the observation bright lines on a less bright background do not make the impression on the mind that dark lines do. When attention is called to their presence they are readily enough seen, even without the aid of a reference spectrum. The photograph, however, brings them into a greater prominence. Dr. Draper then passes from facts to theory. From purely theoretical considerations derived from terrestrial chemistry and the nebular hypothesis, the presence of oxygen in the sun might have been strongly suspected, for this element is currently stated to form eightninths of the water of the globe, one-third of the crust of the earth, and one-fifth of the air, and should therefore probably be a large constituent of every member of the solar system. On the other hand, the discovery of oxygen, and probably other non-metals in the sun, gives increased strength to the nebular hypothesis, because to many persons the absence of this important group has presented a considerable difficulty. At first sight it seems rather difficult to believe that an ignited gas in the solar envelope should not be indicated by dark lines in the solar spectrum, and should appear not apparent exemption of certain substances from the common law of the relation of emission doubt of the existence of an ignited gas in the and absorption, for while there can be no chromosphere giving this line, there is no corresponding dark line in the spectrum of the solar disc. If these observations of Dr. Draper are endorsed, it is impossible to overrate their importance, and those studies which teach us what the sun is made of will be considerably advanced. But this is not all. Not only will our present views of the distribution of the various elemental substances in the sun's atmosphere be entirely bouleversed, but, as may have been gathered from the last quotations, a good deal of physical theory will have to go overboard also. The existence of oxygen in the sun has hitherto been negatived, because there was no correspondence between its bright lines and the dark ones on the solar spectrum. Dr. Draper not only turns the tables upon us, but suggests that there is one law of absorption for metals, another for metalloids. In the case of most of the molecular stages of metalloids this certainly is not true, for the absorption phenomena of iodine, chlorine, sulphur, etc., are among the most beautiful in the whole range of spectrum analysis. It is unfortunate, too, that Dr. Draper has never read, or has forgotten, what has been long written on the most probable position of the metalloids in the solar that is, above (outside) the metals, exactly where, as I have already shown, carbon in all probability has been found. economy to act under the law, "A gas when ignited absorbs rays of the same refrangibility as those it emits." But in fact the substances hitherto investigated in the sun are really metallic vapors, hydrogen probably coming under that rule. The non-metals obviously may behave differently. It is easy to speculate on the causes of such behavior, and it may be suggested that the reason of the non-appearance of a dark line may be that the intensity of the light from a great thickness of ignited oxygen overpowers the effect of the photosphere, just as, if a person were to look at a candle flame through a yard thickness of ignited sodium vapor, he would only see bright sodium lines, and no dark absorption lines. Of course, But my objections do not rest on pure such an expianation would necessitate the theory. I have gone over the ground as hypothesis that ignited gases such as oxygen completely as I have been able, and as a give forth a relatively large proportion of the result, I wish to point out with regard to solar light. In the outburst of T. Coronæ this work of Dr. Draper's, that the photoHuggins showed that hydrogen could give bright lines on a background of spectrum the oxygen lines have been made is not graph in which these comparisons with one which is competent to settle such an extremely important question. Secondly, analogous to that of the sun. However all that may be, I have no doubt of the existence of substances other than oxygen in the sun which are only indicated by bright lines. Attention may be called to the The spectrum between the more marked lines sug I do not find the coincidences between bright solar lines and oxygen lines in that part of the spectrum with which I am most familiar, for the reason that there are no bright lines in this portion of the spectrum, either visible to the eye or in a perfect photograph. Mr. Rutherfurd's magnificently perfect spectrum, going nearly the whole length from O to E, embraces the region included in the photograph of Dr. Draper's. I have carefully gone over a large part of this region line for line, and in no case have I found any true bright line in the sun whatever coincident with any line of oxygen whatever. I do not profess to have gone over the ground in the ultra-violet; but it will appear to me very surprising indeed if, when we go further, and include the H and K lines, Dr. Draper will find any coincidences with bright lines of the sun even there; because when perfect instrumental conditions are brought into play, no bright line whatever exists in that part of the solar spectrum, so far, at all events, as my observations extend. The bright line recorded by Cornu exists outside K. There is an experiment which any one who possesses a spectroscope with three or four prisms can make for himself. Throw the sunlight on to the slit so that the solar spectrum may be visible. Observe the green part. Take the spark in air in an apparatus of the kind to which I have already referred, flood the air with nitrogen, and in the field of view which includes b, and therefore one of the most marked bright lines in the solar spectrum itself, you will find in the same region of the spectrum three or four undoubted lines of oxygen. I have made that experiment, which is quite a simple one, and I find no coincidences in this part of the spectrum between the oxygen lines and the undoubted bright line. gests ribbed structure; hence it is important to know whether the photograph was taken by means of one of the silver-on-glass gratings made by Mr. Rutherfurd. I find that in these, in consequence of the grating being ruled on the back surface of the glass and the double transmission of the light through the plate, there is a considerable formation of Talbot bands, and the solar spectrum is in some regions entirely hidden and absolutely transformed. Lines are made to disappear; lines are apparently produced, so that if one compares a part of the spectrum taken with one of these silveron-glass gratings with an ordinary refraction-spectrum, the greatest precaution is requisite. Indeed, I think that I am not going beyond the mark when I say that the positions of all lines below the third or fourth order of intensity must be received with very great caution indeed when these gratings are employed. So much is this recognized by Mr. Rutherfurd himself, that he is now generously distributing, gratings containing the same number of lines to the inch (17,300, or something like that) engraved on speculum-metal, in order that these defects may be obviated. I do not say that Dr. Draper's alleged discovery is no discovery at all; I say, and I think it is my duty to say it, as I have been occupied in very allied work for some considerable time, that I do not hold it to be established. Dr. Draper must produce a better photograph and must prove his point for the visible spectrum before his discovery can be accepted. I have no doubt that Dr. Draper, in spite of the difficulties he will have to encounter, will carefully attempt this; and I am certain that he will be the first to hail what I have here written with the extremest satisfaction; because his desire, I am sure, is the desire of every true man of science, that the truth should prevail. In any case Dr. Draper has begun work in a branch of the chemical inquiry into solar matters which, up to the present time, has been sadly neglected. The true composition of the sun will never be ascertained till the metalloids have been brought to the test as the metals have been. The reason I have considered Dr. Draper's view at such length is that this is the first serious and prolonged attempt of the kind. There is little doubt that the question I have thought it my duty to raise will be soon settled; and, whatever the result, our knowledge of what the sun is made of is certain to gain by the process. So To sum up, then, in a few words. far as our uncontested knowledge goes the sun is chiefly made of metal, and on this account is strangely different from the crust of our earth in which the metals are in a large minority. Surely it is very wonderful that we should have ever been able to acquire this little item of knowledge, and I feel that the subsequent work which sooner or later will be undertaken to explain this anomaly will land us in a very dreamland of science. It will be found that we poor nineteenthcentury toilers and moilers were but engaged upon the white chamber and not upon the treasury at all! J. NORMAN LOCKYER. Only a view of roy alty in the flesh will remove it, for it is not long since you were yourself in the condition of the child of whom it is recorded that, being taken to the window to see the queen drive through the street, she accounted for the absence of a crown by the supposition that it was lent to the king for that day. Such are perhaps the unsophistical thoughts which you revolve as you watch the glittering throng. What a country is England, that can marshal such an army of carriages on an ordinary summer afternoon! What were the chariots of Sisera of which you heard last Sunday in comparison? count in five minutes more handsome and | about in the regalia. And every carriage filled, as you reasonably suppose, with the highest rank and the greatest wealth of a country where blood is pure and gold is plentiful. Heraldry and eyesight alike are taxed to distinguish a duke's coronet from a mere baron's, and you find that, after the first three attempts to learn off the costumes of the best-dressed ladies, memory refuses the office. You must keep your faculties fresh to observe the princess, every item of whose dress you will be expected to catalogue for the benefit of the womankind at home. You begin to wish for some one who can tell the names of the great peo ple. That man who cursed so audibly when you trod on his toe may have been a great poet. At any rate his language was highly figurative. The wearer of the glit tering hat who canters by on a pony may be a cabinet minister, and you are not sorry when your elbow is grasped by a regular town mouse if the name of so harmless a little beast be really appropriate whose acquaintance you have chanced to make at a country house. He is, however, rather bent on enjoying the astonishment of a country cousin as he sneers at the whole performance. No ladies, he says, of real rank would exhibit their faces in such a way to the vulgar gaze. You thank him mentally for the delicate compliment to yourself; but he goes on to remark that it is only secondrate people who come here to be stared at. There is, he continues, a certain class in London to whom notoriety is pleasant. They have titles among them, and some of them have blue blood in their veins; but for the most part their reputations are damaged, and they are anxious to proclaim the fact to all the world. This, he observes, in spite of your dissent, is a law of society, and these people pretend to constitute society. They are by no means particular as to what they do, or with whom they asso |