December 27, 1894] 



NA TURE 



2 I 



is, so far as at present known, a local, arbitrary, or accidental 

 one, and has not yet been found to recur in any other portion 

 of the globe. 



(i) Droughts or floods may occur every year in some portion 

 of an extensive region, so that it may become possible to predict 

 the occurrence in a special section one year because one has 

 occurred in another section a previous year. Thus, a serious 

 drought in the lower Indian peninsula has, on live occasions, 

 been followed by one in northern India the next year. 



(/') If we had maps of the weather of the whole globe for every 

 month for a long series of years we should, undoubtedly, be able 

 to find many similar coincidences, so that a drought for a given 

 section might be predicttd from the rain-fall, the snow-fall, the 

 temperature, the pressure, or other conditions in a distant part 

 of the globe. As a rule, important climatic crises are the results 

 of changes that have been going on slowly for a long time in 

 distant parts of the earth. The general circulation of the air 

 constitutes a complex system in which the areas of high pressure 

 and dry clear air are the results of slowly descending winds 

 moving toward the equator ; the general rains are formed 

 wherever a descending current of air, a mountain range, or other 

 obstacle has an opportunity to push up the moister air of the 

 earth's surface. From this point of view rainy and dry and cold 

 and hot seasons depend largely upon the varying relations of the 

 upper and lower currents to the continents and even to each 

 other. The long-range prediction of the climate of any season 

 must depend upon the prediction of the general character of the 

 horizontal and vertical movement of the air. Ir. our present 

 geological epoch the continents are permanent features, and «e 

 consider only the changes that take place in the atmosphere, 

 but in studying the climatic changes of earlier geological epochs 

 we have to consider the changes in elevation of the continents 

 themselves. 



(.j) Such apparent connections as that between snow-fall on 

 the Himalayas and the subsequent drought in northern India 

 are not to be thought of as cause and effect respectively. It 

 might be argued that the layer of snow must be evaporated, or 

 melted, thereby absorbirg more heat than would have been 

 required if it had fallen as rain and rapidly drained away ; but 

 this cooling influence is distributed over many weeks, and 

 through the immense quantity of air that has passed over the 

 snow -fields during the winter and the spring, and is thereby 

 rendered too slight to have any great local influence in India. 

 A broader view of the subject shows us that the winter snow- 

 fall and the summer drought are simply two features ol an 

 extensive system of changes in which the whole atmosphere of 

 the earth takes part. The whole globe may be divided into 

 regions where the lower stratum is moving either horizontally 

 or upward or downward, and where the upper stratum has 

 similar diversities of movement. These s)stems of motion 

 determine whether we shall have fair weather or rain, hot 

 weather or cold, fr< m day to day and accumulatively from 

 month to month. New these three movements are related to 

 each other in such a way that the sum total of the energy 

 involved throughout the atmosphere is sensibly constant, while 

 the localities at which the upward and downward motions are 

 taking place are undergoing perpetual changes. 



The centres of high pressure over the oceans and continents 

 slowly sway east and west or north or south ; the paths of the 

 storm-centres vary in a similar manner to suit the changes of 

 these larger areas, and ibe centres themselves move rapialy or 

 slowly in response to these same changes. The air that ascends 

 between the northern and southern tropical regions of high 

 pressure descends scmetinjes in high latitudes, giving them cold 

 weather with rain or snow ; at other times in low latitudes, giving 

 them warm weather with droughts. It mailers not whether 

 the droughts in southern regions chronologically follow or 

 precede the snows of ihe northern regions ; in neither case can 

 either one be spoken of as the cause of the other, but each is 

 in its turn the result of changes in the so-called general circula- 

 tion of the atmosphere. 



This general circulation, wilh all its variations, diurnal, annual, 

 and secular, is dependent uj on the intrinsic density of each 

 portion of the atmo^)jhere and on numerous forces, such as the 

 heat received from the sun, the attraction of the sun, moon, 

 and earth, the resistance offered by the irregular surface or the 

 earth, and the interaction of slow and rapdly moving masses 

 of air. The proper study of ihis subject constitutes the 

 application of hjdrodyramics lo meteorology. 



The meteorological problem has some analogy to that oflered 



NO. 13 I 3, VOL. 51] 



by the hydrsulics of ihe Mississippi River, where cut-ofis, cave- 

 ins, mud-tanks, end crevasses are conlir,uaIly forming and 

 re-formirg. We do ret e>pecl tote alle to foretell when and 

 where these will occur many years in advance, but we do keep 

 a watch en ihe condition of the river; and when conditions are 

 favour able for Ihe formation of any important charge, we watch 

 the pr ocess until Ihe cataslrorhe beccmes more or less immi- 

 nent, and then begin to trake estimates, that may be called 

 predict ions, as to the exact lime and place of the event. 



In m eleorology the best we can do at present in long-range 

 predictions is to chart and study Ihe occurrence of abnormal 

 weather conditions over the whole globe; these phenomena 

 must be inleipieled in the light of all the knowledge we have 

 of Ihe mechanics of the atmosphere, for they are the results of 

 purely mechanical operations covering the whole range of the 

 mechanics of heat, gases, and vapours. 



SCIENTIFIC SERIAL. 



The Quarterly Journal of Microscopical Science, November. 

 — On Julinia, a new genus of compound ascidians 

 from the Antarctic Ocean, by W. T. Caiman (plates 

 1-3). The colony is described as irregularly cylindrical in 

 shape, measuring 78'5 cm. in length, and from l'5 to 25 cm. 

 in diameter ; it was found fl( ating on the surface of the sea in 

 the north of Erebus and Terror Gulf; a consideral le quantity 

 was seen ; no attaching fibres were found, but it was probably an 

 attached form. The species is described 2is jfuUin'a amlralis, 

 and it is provisionally placed in the Distomida?. — Hermaphrodi- 

 tism in mollusca, by Dr. Paul Pelscneer (Ghent) {plates 4-6). 

 Hermaphroditism is found in Ihe Amphineura, the Gastropoda, 

 and the Lamellibranchia. It is not self-sufficient, is sometimes 

 prolandric ; it would seem to the author to be not a primitive 

 arrangement, but to be derived from the unisexual state, and to 

 have been established upon the female organism. — Description 

 of Ihe cerebral convolutions of the chimpanzee known as 

 " Sally," with notes on the convolutions of the brains of other 

 chimpanzees and of two orsngs, by W. Blaxland Benham (plates 

 7-11). — On the inadequacy of the cellular theory cf development 

 and on the early development of nerves, particularly of the third 

 nerve and of ihesjmpathetic, in Elasmobranchii, by .'\dam Sedg- 

 wick, F.R.S. More than len years ago the author called atten- 

 tion to ihe inadequacy of the cellular theory of development : 

 ** Embryonic development can no longer he looked upon as 

 being essentially the formation by fission of a number of units 

 from a single primitive unit, and the coordination and modifica- 

 tion of these units into a harmonious whole. But it must 

 rather be regarded as amulliplicatienof nuclei and a specialisa- 

 tion of tracts and vacuoles in a continuous mass of vacuolated 

 protoplasm.'' And '' although opinions have charged on this 

 important subject, and although there are some who think that 

 they have escapee! from the domination of ihis fetish of their 

 predecessors, yet as a iratler of fact the cellular theory of 

 development is still rampant, still blinds men's eyes to the most 

 patent facts, and still obstructs the way of real progress in the 

 knowledge of structure. " When a student begins his zoology 

 he is told that "ihe various structures present in a protczoon 

 are all parts of one cell, whereas in a metazoon the various 

 parts are composed of groups of cells which differ from one 

 another in structure." When in a later yeriod of his studies he 

 begins embryology, "the importance and distinctness of the 

 cell meels him at every step, from the complete cleavage which 

 he is led lo believe is primitive, lo ihe develoiirent of nerves 

 according lo the views of His." If we take the so-called 

 mesenchjme tissue cf elasmc branch embrjos, it is described as 

 consisting of " blanched cells lying between the eclo- and the 

 endo-derm," while, as a matter of fact, " the separate cells have 

 no exislence," hut "there is a reticulum of a pale non-staining 

 sutslance holding nuclei at its ne des. And far from the 

 develoiment of nerves being an outgrowth of cell-processes 

 from certain central cells, it is simply a differentiation of a 

 substance which was already in position." This important 

 memoir is so cerdensed as to make it extremely difficult to 

 condense it further, tut enough has been given 10 indicate its 

 nature.— On Bin hernia (Oiijiia, n. sp. , from the Gold Co.a;t, by 

 W. B. Btnhani (plate 12). "This large species (20 inches) 

 was found al Axim in Ihe Fanlee ccurlry, on the west coast of 

 Africa. 



