i96 



NA TURE 



[April 21, 1S92 



current between the equator and the doldrums is always from 

 some point near east." ^ 



Here, then, was another actual confirmation of Siemens's 

 theory. Two facts — the diffusion of the Krakatab dust, and 

 Abercromby's observations — supported Siemens's theory of air 

 circulation, yet doubts were not quite removed. Voices were 

 loud against the Krakatab hypothesis and against Abercromby's 

 observations, which allowed another explanation to appear 

 possible. Meteorologists delayed mostly to accept Siemens's 

 theory, because a theoretical, mathematical establishment of it 

 was still lacking. But this was given, as before observed, by 

 Oberbeck, a year or so ago. He arrived at formulae by which 

 Siemens's theory could be reproduced. 



Now, in fact, nothing more was wanting. Siemens's system was 

 confirmed on all sides, by facts and by mathematical treatment. 

 The chief merit for this is certainly due to Oberbeck. Before I 

 bring to your notice the system of the general circulation of the 

 atmosphere, such as it is given by the present state of research, 

 I must allude to one other point in Siemens's exposition — 

 namely, the influence which the general circulation of the 

 atmosphere should have on the origin of cyclones and anti- 

 cyclones in our latitudes. ^ 



The origin of the maxima ought to be due to the fact that the 

 air flowing from lower to higher latitudes is checked in con- 

 sequence of the convergence of meridians, and so produces an 

 increase of pressure. Thus we get the maxima, or anticyclones. 

 If, then, in consequence of this increase of pressure below, air 

 flows out laterally, and, in consequence of the interference, the 

 confined current turns more to the eastward, it must carry the 

 lower strata with it, and give rise to a rarefaction, causing a 

 minimum or cyclone. But this is carried away as a whole by 

 the general current, and thus the progression of cyclones is also 

 explained. 



Siemens holds very strongly to this explanation, principally 

 because it contains a force which explains the energy which is 

 accumulated in anticyclones and cyclones, and which refers 

 finally to the heat of the sun, that maintains the general circu- 

 lation. But I fear he has overshot the mark here. The meridians 

 converge in the southern hemisphere the same as in the northern. 

 Why, then, do almost constant west winds prevail there below, 

 without interference of currents, while with us an almost uninter- 

 rupted system of driving cyclones and anticyclones exists ? Does 

 not this prove that in the formation of cyclones and anticyclones 

 another factor is at work, and might not this perhaps depend on 

 the peculiar distribution of land and water in the northern 

 hemisphere? Upon this point^Siemens will have to modify his 

 views. 



From my analysis we can easily sketch the outline of the 

 general circulation of the atmosphere which corresponds to the 

 present state of the science. 



In consequence of the unequal heating of the sun and of the 

 rotation of the earth, air currents occur at all parts of the globe. 

 These currents are easterly between 35° N. and 35° S. latitude, 

 and westerly outside this zone. 



In the former zone the easterly currents on the earth's surface 

 (in the northern hemisphere) are more north-easterly and 

 northerly the nearer we approach latitude 35°, while in the higher 

 strata they constantly become more southerly as we approach 

 latitude 35°. This explains the circulation between the equator 

 and latitude 35°. A)i upper south-west trade-tvind entirely fails 

 in this region."^ At or near the equator a calm zone must be 

 formed at the earth's surface, where the meridional components 

 of the north-east and south-east trades ascend, but the height 

 of the calm-zone cannot be considerable. Exactly over the 

 calm-zone a pure east wind and the strongest of the whole zone 

 will blow, and the higher the strata under consideration the 

 stronger it will be. 



In latitude 35° N. and S., calms exist at the earth's surface. 

 The air, which has an ascending motion in the equatorial calm, 

 has here a descending movement. But above, the current 

 directed polewards continues to exist. Outside this great 

 region, to the north and south, west winds will prevail ; while 

 above, the south-west (or the north-west) trade-wind blows, 

 which in higher latitudes will become more and more westerly. 

 At the earth's surface, air in south-westerly or north-westerly 



1 Mr. Abercromby afterwards modified this opinion (Nature, vol. xxxix. 

 p. 437). — Translator. 



2 This statement as to the failure of the upper south-west trade-wind 

 between the equator and lat. 35° was afterwards modified (see Das Wetter, 

 1890, p. 158). — Translatoy . 



motion flows from the zone of high pressure at latitude 35°, 

 which becomes more westerly with increasing latitude. At a 

 mean altitude, however, air flows again from the poles towards 

 latitude 35' as a north- west wind. 



This is the picture of the general circulation of the atmosphere 

 according to the latest researches. There is undoubtedly much 

 to be completed, and it presents many dark points which remain 

 to be cleared up, but on the whole it possesses every guarantee 

 of truth and reality, and will doubtless soon be generally accepted. 

 The question of the effect upon cyclones and anticyclones of 

 this general circulation of the atmosphere will certainly come to 

 the front, but we shall have to wait for a considerable time for a 

 satisfactory solution of the problem. 



RELATION OF VOLTAIC ELECTROMOTIVE 

 FORCE TO MOLECULAR VELOCITY. 



TN a recent research published in vol. viii., p. 63, of the Pro- 

 ceedings of the Birmingham Philosophical Society, 1892, it 

 is shown, by means of an extensive series of sixty-four tables of 

 measurements oiniean volta electromotive force, that the dilution 

 of the liquid of a voltaic cell by means of water or alcohol, the 

 liquefaction of either the positive or negative metal of the cell by 

 means of mercury, the dilution of either of these amalgams by 

 means of mercury, or the dilution of one solid metal by means 

 of another in an alloy, is universally attended by an increase of 

 7nean electromotive force of the diluted and diluting substances, 

 and consequently also of the actual electromotive force of the 

 diluted one, provided that in all cases no chemical union or 

 other chemical change occurs in the mixture. The manifest 

 explanation of this extensive general result is that, by the act of 

 solution or dilution, the molecules of the active substance are 

 separated farther apart, and consequently acquire increased 

 velocity of motion. In proportion, however, as chemical union 

 occurs, the gain of electromotive force diminishes and is con- 

 verted into a loss, and the loss is larger in proportion as the 

 chemical union is stronger. The method enables chemical com- 

 pounds in alloys, amalgams, and electrolytes to be distinguished 

 from mere mechanical mixtures, G, Gore. 



NO. II 73, VOL. 45] 



SCIENTIFIC SERIALS. 



In the Botanical Gazette for February and March, Miss Alice 

 Carter has an interesting paper on evolution in methods of 

 pollination. She points out that the larger proportion of 

 Monocotyledons are either anemophilous or hydrophilous, and 

 this is undoubtedly an earlier method of pollination than the 

 entomophilous. Of the twenty-three natural orders which com- 

 prise more than 1000 species, only five are characterized by 

 inconspicuous flowers. Of these, four, viz. the Cyperaceae, 

 Graminese, Urticacese, and Piperacese, are probably ancestral 

 types, the fifth, Euphorbiaceaa, degenerate. It is probable that 

 the. period of the appearance of Dicotyledons was also that of 

 the development of our great groups of insects. The first step 

 towards the attraction of insects was probably the colouring of the 

 stamens, as in Thalictrum and Plantago ; then the development 

 and colouring of the corolla, and the production of saccharine 

 secretions. The most highly developed orders appear to be 

 those in which the number of parts in a floral whorl is small, as 

 the Violacete, Compositas, Labiatse, and Scrophulariacese.— Mr. 

 P. H. Rolfs has an article on the Seed-coats of Malvaceae ; and 

 Mr. Chas. Robertson continues his researches on Flowers and 

 insects. 



In the Journal of Botany for March and April, Mr. E. A. L. 

 Batters describes and figures a new marine alga, Gonimophylliim 

 Buffhami,ihc type of anewgenus. Itbelongs to the Delesseriaceae, 

 an order of Floridese, and is epiphytic on Niiophyllum lacera- 

 tum, being in fact nearly allied genetically to its host-plant. It 

 was obtained from the coast near Deal. — Mr. R. J. Harvey 

 Gibson describes the hitherto unknown antherids of Polysiphonia 

 elongella, the mode of escape and conjugation of the zoogametes 

 of Enteromorpha compressa, and the mode of development of the 

 spores of British marine species of Chantransia.—'Mx. E. G, 

 Baker continues his Synopsis of the genera and species of 

 Malvese : and Mr, W. H. Clarke his First records of British 



