Jan. II, 1877I 



NATURE 



239 



plants, and mostly in the foliage leaves, so that creeping 

 insects satisfy here their need of food, and do not trouble 

 themselves about reaching the flowers higher up, and thus 

 these remain protected from their visits. 



" From the foregoing obervations," says M. Kemer, 

 " it will sufficiently appear that the relations of plant-form 

 to that of animals living at the expense of plants. are far 

 more manifold than has hitherto been supposed, and that 

 especially numerous formations in foliage-leaves and stem 

 are so far of biological significance that by them protection 

 is afforded to the flowers against the prejudicial visits of 

 certain animals. Where the attacking animals are absent 

 this defence is also, naturally, useless, and therefore all 

 these formations are properly to be regarded as means 

 of protection only for those plant-stocks which occur in 

 their original region — in the region where the species to 

 which they belong has arisen. In another place they are 

 perhaps not means of defence ; indeed they may even 

 be of disadvantage, or their formation there is at least 

 something superfluous, not in the economy of the plant, 

 and as a matter of course, these disadvantageous, because 

 not economically organised plants, when they come under 

 conditions which are not in harmony with their form, are 

 driven out of the field by competitors that are more 

 advantageously organised. 



" If, for example, a plant species comes, in course of its 

 migrations, into a region in which it is exposed to other 

 attacks, or if the external relations in the place where the 

 species arose (and with which it was formerly in agree- 

 ment) are altered, it may become more and more rare, 

 and gradually quite die out. Among these changes of 

 external relations, however, are to be understood not 

 merely changes of climate j a not less important part is 

 played by the changes which o:cur in the animal world in 

 a particular region. Apart altogether from changes in the 

 extent of distribution of animals, the animals vary as well 

 as the plants, and individual varieties, which occur with 

 new characters that are advantageous relatively to given 

 external conditions, may become the starting point of 

 new species. What is of advantage, however, to the 

 animals which attack the plants, constitutes, as a rule, a 

 disadvantage for the attacked plant, and it is therefore not 

 only possible, but in course of time it has actually often 

 happened that in consequence of the multiplication of an 

 advantageously organised animal form in a certain region, 

 some plants in this same region having their flowering 

 function destroyed, and their formation of seeds hindered, 

 have disappeared gradually from the scene. 



"While, on the one hand, the dying out of certain species 

 with altered external relations, is at once explained by 

 changes in the attacks of animals, the same relations, on 

 the other hand, afford an explanation of the phenomenon, 

 that under similar external conditions, plant species, 

 which, with reference to other characters, are classed under 

 the most different genera and families, do yet in certain for- 

 mations agree Avith each other. Only the advantageous 

 forms can maintain themselves, and only those individual 

 varieties which appear with characters that are advanta- 

 geous with reference to the conditions presented by the loca- 

 lity and position become the starting-points of new species. 

 Since, however, the creation of new species in this way may 

 occur in the most different plant-families, it is explicable 

 that we find, e.g.^ in one floral region, very many species 

 of the most different stocks guarded with prickles, in 

 another floral region such species furnished pre-eminently 

 with flowers very rich in nectar, and that often even the 

 character of the whole vegetation is determined by the 

 preponderance of plants with like formations. Owing to 

 the fact that the variety of the means of protection, as well 

 as of the means of attraction is very great, and that 

 through formations of the most different kind the same 

 result can be reached, this conformity is again, of course, 

 greatly limited. Indeed, precisely by this circumstance that, 

 against the same prejudicial attacks, very different forma- 



tions may serve as equally good means of defence, is the 

 phenomenon explained that frequently several species of 

 a family occur beside one another, without entering into 

 competition in this relation, because the species, each 

 after its own fashion, possess equal advantages." 



THE ACTION OF THE WINDS IN DETER- 

 MINING THE FORM OF THE EARTH^ 



TN view of the most recent discoveries in the region of physics, 

 especially with regard to the nature and properties of forces, 

 it became necessary eo ipso for dynamical geology to give up as 

 unsatisfactory the division of geological forces into "igneous" 

 and "aqueous," and to substitute a division of them into 

 " primary" and " secondary" ; of which the former explain all 

 the motions which we observe on and in the earth, according to 

 their origin and nature ; while the others — one might call them 

 "agencies" to distinguish them from the first — would teach us 

 what and how great changes in the figure of the earth's surface 

 are produced by the bodies so moved, through reciprocal action 

 on each other. Sensible of this inevitable reform in dynamic 

 geology, the author of an es?ay entitled "The Action of the 

 Winds on the Configuration of the Earth," sought to call atten- 

 tion to the gaps hitherto existing in physical geography, and 

 especially to show what a mighty and yet hitherto very little 

 observed agent the wind is, considered as one of these secondary 

 geological forces. In the following paper the author offers to 

 the readers of NiVTURE a resume of his memoir. 



It is at once evident and conformable to nature that the winds 

 are to be regarded, in the first instance, as a proof of the unequal 

 insolation at different points of the earth's surface, but, in their 

 direction and variation, they are immediately influenced now by 

 the position of the sun, now by the earth's rotation and the dis- 

 tribution of the solid and the liquid ; that the winds are, on the 

 one hand, a product of these geophysical actions, and, on the 

 other, become a special factor, of which not only the meteorolo- 

 gist, but also, in front rank, the geologist, is called on to take 

 account. Since, that is to say, it is purely the winds which 

 determine the condition of moisture of the atmosphere, and have 

 to perform the role of distribution of rain over the entire sur- 

 face of the earth, but at the same time, in their constant circu- 

 lation from the equator to the poles and from the poles to the 

 equator, represent an imposing motive force, it is obvious that 

 to be able to prove and establish more fully their geological 

 rdle, one must consider them in this twofold relation ; on the 

 one hand as a climatic-meteoric, on the other as a mechanical 

 agent. Accordingly the essay referred to treats, in its first part, 

 of the chmatic-meteoric, in the second, of the mechanical action 

 of the winds ; while the third part comprehends those actions 

 of the winds -which they perform indirectly either in meteoro- 

 logical or in mechanical relation. 



More particularly the First Part is concerned with the charac- 

 teristics of the two principal wind systems, the polar and equa- 

 torial currents, and with their reaction on those continents and 

 mountain-chains, by which, in their typical course — as is mani- 

 fest on oceans and neighbouring coasts, especially west coasts, 

 of continents — they are variously disturbed. The equatorial 

 currents here appear as properly the distributors of precipitation, 

 and therefore as the principal factors by which the transporting 

 power of flowing water, or generally the levelling action of water 

 on the earth's surface, is produced. The polar currents, on the 

 other hand, discover a tendency to act contrary to the work of 

 the equatorial currents, that is, to restore the precipitated water 

 in vapour form to the atmosphere, and generally to further eva- 

 poration. In view, however^ of the fact that not all the water, 

 which by action of the winds is precipitated on the solid land, 

 returns to the ocean or the atmosphere, these two air-currents 

 together appear to be similarly empowered to empty entirely, 

 some time, the immense water-basin of the earth from which 

 they continually procure anew their freight of water, and mean- 

 while to continuously lower the sea-level, through by a very 

 small quantity, and therefore to take a prominent part in the 

 so-called secular elevation of continents. 



These two air-currents, inleed, are not every where and always 

 true to the character just given. On the contrary, when they 

 have to accomplish a great work, and especially when a polar 

 current has to rise over a lofty mountain, or an equatorial current 



I Abstract, by Dr. Francis Czerny, of a memoir of his in the 48th 

 supplementary number of Petermann's Mittlieilungen, 



