Oct. 5, 1882] 



NATURE 



547 



not very obvious manner, by means of certain backward 

 forces arising from induced whirl-systems. Whether 

 some small portion of the phenomenon may not be due 

 to an induced reflex action, is a point worthy of investiga- 

 tion, but the major portion is generally admitted to be 

 due to a principle with which, the author, since he entirely 

 omits all reference to it, is apparently unfamiliar, viz. that 

 the pressure both of compressible and incompressible 

 fluids is diminished by an increase of velocity. A con- 

 clusion drawn by the author from an experiment on p. 

 276 is similarly invalidated by the omission of the same 

 principle. 



The way in which fluid moves in pipes or channels is 

 described in Chapter VII., and is concluded to be by 

 rolling contact on a continuous system of lateral whirl- 

 rings, " these being alternately collected by reflex action, 

 that converts these whirls into loops, which permit the 

 deflected fluid to re-enter (in a hypercycloidal curve) the 

 central system by traction." 



The same principle of rolling contact and the develop- 

 ment of whirl-systems is, in Chapter VIII., applied to the 

 motions of solids through fluids, more particularly of 

 ships, through water. The eddies, for example, which we 

 ordinarily observe at the rear of boats are regarded by 

 Mr. Stanley, not as resulting from the meeting of two 

 relatively opposed currents, but as friction rollers engen- 

 dered by the passage of the body through the liquid. 

 The general effects of rudders on the motion of ships, 

 and the peculiar cases noticed by Prof. Osborne Reynolds 

 and others, are ascribed to the position and influence of 

 such whirls, and not to the mere deflection of stream 

 lines. Although a good deal of what the author says on 

 this point is, as he admits himself in the preface, very 

 speculative, and though the theoretical action from which 

 it all proceeds is not very plain, there is much that is 

 suggestive and worthy of study. 



Section II. is devoted to a consideration of Oceanic 

 and Aerial Systems of Circulation, which are assumed to 

 be gigantic whirl systems arising from the projection of 

 water within quiescent water, or against solid areis of re- 

 sistance such as capes and promontories. A good deal 

 of the matter usually found in treatises on physical geo- 

 graphy is here reproduced, as to the general forces in 

 action to disturb equilibrium, but in the case of general 

 oceanic circulation, too much importance is, we think, 

 attached to the thermal causes of circulation discussed 

 by Lenz and Dr. Carpenter, and too little notice taken of 

 the effect of prevailing winds in causing at least superficial 

 ocean currents. Nothing very fresh is adduced in ex- 

 planation of the causes of the currents as they are at pre- 

 sent known. The main currents, such as the Atlantic 

 equatorial, are assumed to exist, and all the author does, 

 is to try and arrange them as large circles or whirls to 

 suit his whirl theo-y, and which please the eye just in 

 proportion as they diverge from the truth and irregularity 

 of nature. 



We do not doubt that the currents occasionally take the 

 form of whirls such as those exhibited by the author, since 

 their deflection by continents and the continuity of the 

 circulation, requires the water to flow more or less in 

 closed curves, but we cannot agree with the author's view 

 that the Southern Polar drift current is simply a huge 

 whirl, set spinning round by the tangential forces exerted 



by the whirl systems of the South Atlantic and South 

 Pacific. We prefer the simpler and more rational view 

 that it is a result of the constant and similarly directed 

 wind system of that region. Another view indulged in 

 by Mr. Stanley on p. 377 that the southward pointing of 

 the continents is due to action of ocean currents acting 

 through countless ages, is not more probable than the 

 astronomical hypothesis that this is due to a northward 

 motion of the earth in space. Besides, the abyssal cha- 

 racter of marine basins shown by Sir Wyville Thomson, 

 forms a positive objection to any such notion. 



The author's views of atmospheric circulation are not 

 happy. For example, in his chart of the general system 

 of air motion, which he tries to reduce to two large "ellip- 

 soidal whirls" having their southern foci in June, near 

 the east of the United States and China respectively, and 

 which correspond roughly to the general motions traceable 

 over the sea areas, we find the motion of the air over the 

 western part of North America and the Indian peninsula 

 distinctly contrary to what is known to occur at this 

 season from observation. 



It would indeed be a tedious task to point out all the 

 questionable hypotheses or erroneous conclusions with 

 which this part of the work teems. One or two, how- 

 ever, we cannot overlook. For example, the absurd idea 

 that the prevailing south-west winds over the flat plains 

 of Northern Europe, are an indraught to feed the cold and 

 therefore contractile area of Central Europe and Asia- 

 The author travels in vain all round Asia, in search of a 

 current to satisfy the cravings of this contractile area ; 

 and this is the only one which has an approach to the 

 necessary direction. We need hardly say that we are 

 totally unable to credit our south-west winds with the 

 ability to perform such a feat. Areas of cold air, are areas 

 of contraction in a vertical, not horizontal, direction, and 

 are fed by upper, not lower currents. 



In another place we are told that directly under the 

 sun in the tropical region there should be no cloud, owing 

 to the vapour remaining uncondensed under vertical solar 

 rays. At about 30 N. and S., however, there shoulf be 

 bands of cloud and constant precipitation. Now, as a 

 matter of fact we know that the actual conditions are pre- 

 cisely the reverse of these. Thus in the tropics, whenever 

 the sun becomes vertical over any region, he is invariably 

 accompanied sooner or later by a band of cloud and 

 consequent rainfall, while the areas 30 N. and S. are 

 notably those of small precipitation and almost constant 

 sunshine. 



Again, we cannot agree with the statement on p. 444 

 that " all cloud systems by their superior weight will be 

 descending/' or that "condensation of vapour causes a 

 descending area." The very continuity of the existence 

 of a cloud is dependent on its forming part of an 

 ascending area, since by well-known physical principles, 

 if such an area once began to descend, the cloud would, 

 cateris paribus, almost immediately be re-absorbed and 

 become invisible. 



Another conclusion of the author's is in striking opposi- 

 tion to the doctrine ordinarily held by meteorologists ; 

 viz. that the cyclonic area is one of ascent, and the anti- 

 cyclonic one of descent. Mr. Stanley says : " Upon the 

 principle of whirl motions they would be the reverse of 

 this," but we entirely fail to see how or why. 



