Aug. 26, 1875] 



NATURE 



349 



likewise aware that these currents are caused by the unequal 

 temperature of the earth ; they are in truth convection- currents, 

 and their course is detern-.ined by the positions of the hottest and 

 coldest parts of the earth's surface. We may expect them, 

 therefore, to have a reference not so much to the geographical 

 equator and poles as to the hottest and coldest regions. In 

 fact, we know that tlie equatorial regions into which the trade 

 winds rush and from which the anti-trades take their origin, have 

 a certain annual oscillation depending upon the position of 

 the sun, or in other words upon the season of the year. We 

 may likewise imagine that the region into which the upper- 

 currents pour themselves is not the geographical pole, but the 

 pole of greatest cold. 



In the next place we may imagine that these currents, as far as 

 regards a particular place, have a daily oscdlation. This has, I 

 believe, been proved as regards the lower currents or traJe- 

 winds which are more powerful during the day than during the 

 night, and we may therefore expect it to hold good wiih regard 

 to the upper-currents or anti-trades ; in fact, we cannot go 

 wrong in supposing that they also, as regards any particular 

 place, exhibit a daily variation in the intensity with which 

 they blow. 



Again, we are aware that the earth is a magnet. Let us not 

 now concern ourselves about the origin of its magneiism, but 

 rather let us take it as it is. We muse next bear in mind that 

 rarefied air is a good conductor of electricity ; indeed, according 

 to recent experiments, an extremely good conductor. The return 

 trades that pass above from the hotter equatorial reg ons to the 

 poles of cold, con.-isting of moist rarefied air, are ihertfure to be 

 regarded in the light of good conductors crossmg hues of mag- 

 netic force ; we may therefore expect them to be the vehicle of 

 electric currents. Such electric currents will of course react on 

 the magneiism of the earth. Now, since the vclucity of these 

 upper currents has a daily variation, their influence as exhibited 

 at any place upon the magnetism of the earth may be expected 

 to have a dai.y variation also. 



The question thus arises. Have we possibly here a cause 

 which may account for the well-known daily magnetic varia- 

 tion ? Are the peculiarities of this variation such as to corre- 

 spond to those which mi^ht be expected to belong to such electric 

 currents? I think it may be said that as iar as we can judge 

 there is a likeness of this kind between the peculiarities of these 

 two things, but a more piolonged scrutiny wdl of course be 

 essential before we can be absolutely certain that such currents 

 are fitted to produce the daily variation of the earth's mag- 

 netism. 



Besides the daily and yearly periodic changes in these upper 

 convection currents we should also expect occasional and abrupt 

 changes forming the counterparts of those disturbances in ihe 

 lower strata with which we are familiar. And these may be 

 expected in like manner to produce non-periodic occasional dis- 

 turbances of the magnetism of the earth. Now it is well known 

 that such disturbances do occur, and further that ihey are most 

 frequent in those years when cyclones are most frequent, that is 

 to say in years of maximum suuspots. In one woro, it apptais 

 to be a tenable hypothesis to attribute at least the most promi- 

 nent magnetic clianges to atmospheric motions taking place in 

 the upper regions of the atmosphere where each moving stratum 

 of air becomes a conductor moving across lines of magnetic force ; 

 and it was Sir Wm. Thomson, I believe, who first suggested that 

 the motion of conductors across the hues of the earth's magnetic 

 force must be taken into account in any attempted explanation 

 of terrestrial magnetism. 



It thus seems possible that the excessive magnetic disturbances 

 which take place in years of maximum sunspots may not be 

 directly caused by any solar action, but ujay rather be due to ihe 

 excessive meteorological disturbances which are likewise charac- 

 teristic of such yeais. On the other hand, that magnetic and 

 meteorological influence which Mr. Broun has found to be con- 

 nected with the sun's rotation points to some unknown direct 

 effect produced by our luminary, even if we imagine that the 

 magnetic part of it is cauved by the meteorological. Mr. Broun 

 is of opinion that this effect of the sun does not depend upon the 

 amount of spots on his surface. 



In the next place, that influence of the sun in virtue of which 

 we have most cyclones and greater meteorological disturbance in 

 the years of maximum spots cannot, I think (as far as we know 

 at present), be attributed to a change in the heating power of 

 the sun. We have no doubt traces of a temperature effect which 

 appears to depend upon the sun-period, but its amount is very 

 small, whereas the variation in cyclonic disturbance is very great. 



We are thus tempted to associate this cyclone producing in- 

 fluence of the sun with something different from his light and 

 heat. As far, therefore, as we can judge, our luminary would 

 appear to produce three distinct effects upon our globe. In the 

 first place, a magnetic and meteorological efftct, depending 

 somehow upon his rotation : secondly, a cyclonic effect de- 

 pending somehow upon the disturbed state of his surface ; and 

 lastly, the well-known light and heat effect with which we all 

 are familiar. 



If we now turn to the sun we find that there are three distinct 

 forms of motion which animate his surface particles. In the first 

 place, each particle is carried round by the rotation of our 

 luminary. Secondly, each particle is influenced by the gigantic 

 meteorological disturbances of the surface, in virtue of which it 

 may acquire a \elocity rangmg as high as 130 or 140 miles a 

 second; and lastly, each particle, on account 01 its high tempe- 

 rature, is vibrating wiih extreme rapidity, and the energy of these 

 vibrations communicated to us by means of the ethereal medium 

 produces the well-known light and heat efl^ect of the sun. 



Now, is it philosophical to suppose that it is only the last ot 

 these three motions that influences our earth, while the other 

 two produce absolutely no effect ? On the contrary, we are, I 

 think, compelled by considerations connected with the theory of 

 energy, to attribute an influence, whether great or small, to the 

 first two as well as to the last. 



W^e are thus led to suppose that the sun must influence the 

 earth in three ways, one depending on his rotation, another on 

 his meteorological disturbance, and a third by meaijS of the 

 vibrations of his surface particles. 



But wo have already seen that, as a matter of fact, the sun 

 does appear to influence the earth in three distinct ways — one 

 magnetically and meteorologically, depending apparently on his 

 period of rotation ; a second cyclonically, depending apparently 

 on the meteorological conditions of his surface ; and a third, by 

 means of his light and heat. 



Is this merely a coincidence, or has it a meaning of its own ? 

 We cannot tell ; but 1 may venture to think that in the puisuic 

 of this problem we ougiit to be prepared at leist to admit the 

 pos>ibility of a three-iold influence of the sun. 



Even from this very meagre sketch of one of the most inter- 

 esting and important of physical problems, it cannot fail to 

 appear that while a good deal has already been done, its progress 

 in the future will veiy greatly depend on the completeness ol ti e 

 method and continuity of the observations by which it is pur- 

 sued. We have here a field which is of importance not inertly 

 to one, or even to two, but almost to evciy conceivable brancti 

 of research. 



Why should we not erect in it a sort of science exchange into 

 which the physicist, the chemist, and the }.eologist may each 

 cairy the fruits of his research, receiving back in return some 

 suggestion, some principle, or some other scientific commod.ty 

 that will aid him in his own field. But to establish such a mart 

 must be a national undertaking, and already several naiions 

 have acknowledged their obligations in this respect. 



Already the German Government have established a Sonnen- 

 warte, the mere building and equipment of which is to cost 

 B laige sum. With an appreciation of what the spectroacope li is 

 done for this inquiry, the first directorship was offered to KircM- 

 holf, u.id on Iuj clc^l.uing it, llcrr Vogel has been placed in 

 charge. In France also a physical observatory is to be erected 

 at Fontenay, on an equal, if not greater scale, of which Jan sen 

 has already accepted the directorship ; while in Italy there are 

 at least three observatories exclusively devoted to this branch of 

 reseach. Nor must we forget that in this country the new 

 observatory at Oxford has been so arranged that it can be 

 employed in such inquiries. But what has England as a nation 

 done ? 



Some years since, at the Norwich meeting of this Association, 

 a movement was set on foot by Col. Strange which resulted 

 in the appointment of a Royal Commission on the advance- 

 ment of science, wiih the Duke of Devonshire as chairman. This 

 Commission have quite recently reported on the steps that ought 

 in their opinion to be taken for ttie advancement ol scientific 

 research. 



One of their recommendations is expressed in the following 

 words : — 



" Important classes of phenomena relating to physical meteoro- 

 logy and to terrestiial and astronomical physics require observa- 

 tions of such a character that they cannot be advantageously 

 carried on otherwise than under the direction of Government. 

 Institutions for the study of such phenomena should be main- 



