348 



NATURE 



\Aug. 26, 1875 



probably disappear on further examination. This method has 

 already afforded us a means of determining the relative amount 

 of the various metallic vapours in the sun's atmosphere. Thus, 

 in some instances all lines are reversed, whereas in others the 

 reversal extends only to a few of the longer lines. 



Several new metals have thus been added to the list of those 

 previously detected in the solar atmosphere, and it is now certain 

 that the vapours of hydrogen, potassium, sodium, rubidium, 

 barium, strontium, calcium, magnesium, aluminium, iron, man- 

 ganese, chromium, cobalt, nickel, titani>jm, lead, copper, cad- 

 mium, zinc, uranium, cerium, vanadium, and palladium occur in 

 our luminary. 



I have spoken hitherto only of telescopic spectroscopy ; but 

 photography has been found capable of performing the same 

 good service towards the compound instrument consisting of the 

 telescope and its attached spectroscope, which it had previously 

 been known to perform towards the telescope alone. It is of no 

 less importance to secure a permanent record of spectral pecu- 

 liarities than it is to secure a permanent record of telescopic 

 appearances. This application of photography to spectrum 

 observations was first commenced on a sufficient scale by Mr. 

 Rutherford, of New York, and already promises to be one of 

 I he most valuable aids in solar inquiry. 



In connection with the spectroscope I ought here to mention 

 the names of Respighi, and Secchi, who have done much in the 

 examination of the solar surface from day to day. It is of great 

 importance to the advancement of our knowledge, that two such 

 competent observers are stationed in a country where the climate 

 is so favourable to continued observation. 



The examination of the sun's surface by the spectroscope sug- 

 gests many interesting questions connected with other branches 

 of science. One of these has already been alluded to. I may 

 mention two others put by Mr. Lockyer, premising, however, 

 ihat at present we are hardly in a position to reply to them. 

 It has been asked whether the very high temperatures of the 

 sun and of some of the stars may not be sufficient to produce the 

 disassociation of those molecular structures which cannot be 

 disassociated by any terrestrial means ; in other words, the ques- 

 ti m has been raised, whether our so-called elements are really 

 elementary bodies. 



A third question is of geological interest. It has been asked 

 whether a study of the solar atmosphere may not .throw some 

 light upon the peculiar constitution of the upper strata of the 

 earth's surface, which are known to be of less density than the 

 average interior of our planet. 



If we have learned to be independent of total eclipses as far 

 as the lower portions of the solar atmosphere are concerned, it 

 must be confessed that as yet the upper portions — the outworks 

 of the !-un — can only be successfully approached on these rare 

 and precious occasions. Thanks to the various Government 

 expeditions despatched by Great Britain, by the United States, 

 and by several Continental nations— thanks, also, to the exer- 

 tions of Lord Lindsay and other astronomers — we are in the 

 possession of definite mformation regarding the solar corona. 



In the first place, we are now absolutely certain that a large 

 part of this appendage unmistakably belongs to our luminary, 

 and in the next place, we know that it consists, in part at least, 

 of an ignited gas giving a peculiar spectrum, which we have not 

 3 et been able to identify with that of any known element. 

 '1 he temptation is great to associate this spectrum with the 

 j>iesence of something lighter than hydrogen, of the nature of 

 which we are yet totally ignorant. 



A peculiar physical structure of the corona has likewise been 

 suspected. On the whole, we may say that this is the least 

 known, while it is perhaps the most interesting, region of solar 

 research ; most assuredly it is well worthy of further investiga- 

 tion. 



If we now turn our attention to matters nearer home, we find 

 that there is a difficulty in grasping the facts of terrestrial 

 meteorology no less formidable than that which assails us when 

 we investigate solar outbreaks. The latter perplex us because 

 the sun is so far away and because also his conditions are so 

 riilTereiit from those with which we are here familiar j while on 

 the other hand, the former perplex us because we are so inii- 

 niately mixed up with them in our daily lives and actions; 

 because, in fact, the scale is so large and we are so near. The 

 result has been that until quite recently our meteorological 

 operations have been conducted by a band of isolated volunteers 

 individually capable and skilful, but from their very isolation 

 incapable of combining together with advantage to prosecute a 

 scientific campaign. Of late, however, we have begun to per- 



ceive that if we are to make any advance in this very interesting 

 and practical subject, a different method must be pursued, and 

 we have already reaped the first fruits of a more enlightened 

 policy ; already we have gained some knowledge of the constitu- 

 tion and habits of our atmosphere. 



The researches of Wells and Tyndall have thrown much light 

 on the cause of dew, Humboldt, Dove, Buys Ballot, Jelinek, 

 Quetelet, Hansteen, KupfTer, Forbes, Welsh, Glaisher, and 

 others have done much to give us an accurate knowledge of the 

 distribution of terrestrial temperature. Great attention has like- 

 wise been given to the rainfall of Great Britain and Ireland, 

 chiefly through the exertions of one individual, Mr. G. J. 

 Symons. 



To Dove we are indebted for the law of rotation of the wind, 

 to Redfield for the spiral theory of cyclones, to Francis Gaiton 

 for the theory of anti-cyclones, to Buchan for an investigation 

 into the disposition of atmospheric pressure which precedes 

 peculiar types of weather, to Stevenson for the conception 

 of barometric gradients, to Scott and Meldrum for an acquaint- 

 ance with the disposition of winds which frequently precedes 

 violent outbreaks ; and to come to the practical application of 

 laws, we are much indebted to the late Admiral Fitzroy and the 

 s-ystem which he greatly helped to establish for our telegraphic 

 warnings of coming storms. 



Again, the meteorology of the ocean has not been forgotten. 

 The well-known name of Maury will occur to every one as that 

 of a pioneer in this branch of inquiry. Fitzroy, Leverrier, 

 Meldrum, Toynbee, and others have likewise done much ; and it 

 is understood that the meteorological offices of this and other 

 maritime countries are now busily engaged upon this important 

 and practical subject. Finally, the movements of the ocean and 

 the temperatures of the oceanic depths have recently been 

 examined with very great success in vessels despatched by her 

 Majesty's Government ; and Dr. Carpenter has by this means 

 been able to throw great light upon the convection currents 

 exhibited by that vast body of water which girdles our globe. 



It would be out of place to enter here more minutely into this 

 large subject, and already it may be asked what connection has 

 all this with that part of the address that went before it. 



There are, however, stiong grounds for supposing that the 

 meteorology of the sun and that of the earth are intimately con- 

 nected together. Mr. Broun has shown the existence of a 

 meteorological period connected apparently with the sun's rota- 

 tion ; five successive years' observations of the barometer at 

 Singapore all giving the period 25 74 days. Mr. Baxendell, of 

 Manctiester, was, I believe, the first to show that the convection 

 currents of the earth appear to be connected somehow with the 

 state of the sun's surface as regards spots ; and still more re- 

 cently, Mr. Meldrum, of the Mauritius Observatory, has shown 

 by a laborious compilation of ships' logs and by utilising the 

 meteorological records of the island, that the cyclones in the 

 Indian Ocean are most frequent in years when there are most 

 surspots. He likewise affords us grounds for supposing that the 

 lainlall, at least in the tropics, is greatest in years of maximum 

 solar disturbance. 



M. Poey has found a similar connection in the case of the 

 West Indian hurricanes ; and finally, Piazzi Smyth, Stone, 

 Koppen, and still more recently, Blaaford, have been able to 

 brmg to light a cycle of terrestrial temperature having apparent 

 reference to the condition of the sun. 



Thus, we have strong matter-of-fact grounds for presuming a 

 connection between the meteorology of our luminary and that of 

 our planet, even although we are in complete ignorance as to the 

 exact nature of this bond. 



If we now turn to terrestrial magnetism the same coimection 

 becomes apparent. 



Sir Edward Sabine was the first to show that the disturbances 

 of the magnetism of the earth are most violent during years of 

 maximum sunspots. Mr. Broun has shown that there is likewi.-e 

 a reference in magnetic phenomena to the period of the sun's rota- 

 tion about his axis, an observation recently confirmed by Horn- 

 stein ; and still more recently, Mr. Broun has shown that the 

 moon has an ac ion upon the earth's magnetism which is not 

 altogether of a tid^l nature, but depends, in part, at least, upon 

 the relative position of the sun and moon. 



I must trust to your forbearance if I now venture to bring 

 forward considerations of a somewhat speculative nature. 



We are all familiar with the generalisation of Hadley, that is 

 to say we know there are under-currents sweeping along the 

 surface of the earth from the poles to the equator, and upper- 

 currents sweeping back from the equator to the poles. We are 



