304 



SCIENCE. 



[Vol. XIX. No 486 



air, whither we follow it in an ascending current. It being per- 

 ceived that its departure from the 30th parallel tended to produce 

 a vacuum on that line, this current of air flows back again as 

 upper strata in a south-west direction, obeying the same law which 

 gives a western component of motion to the trades ; . when it 

 reaches the parallel of 30° and then meets the other body from 

 the equator, its further progress in that direction ceases, and it 

 pours down to the surface and begins its circuit again. The 

 northern limit of this motion is believed to be about the 60th 

 parallel. So here we have another body of air, similar to that 

 within the tropics, moving in a continuous circuit, but in opposite 

 directions. For similar reasons, the atmosphere between latitude 

 60° and the pole will also move in a circuit between those points, 

 only the direction of motion will be the reverse of that in the 

 temperate zone. The coldest air in this northern zone being pre- 

 sumably at the pole, and therefore heaviest, will sink down to the 

 surface and move southward with a western component, obeying 

 the same laws heretofore given. When it reaches latitude 60°, it 

 will meet the current from the south, rise to the upper strata, and 

 flow back to the pole. 



These several motions and the entire circulation in the northern 

 hemisphere may be better understood by reference to the follow- 

 ing figure : — 



N.POLE 



The arrows at the right band show the direction of the surface 

 fllow, and those at the left indicate the direction of the upper 

 strata, in the several zones. 



It is to be understood, of course, that the foregoing theory is 

 based upon the assumption of an earth with a homogeneous sur- 

 face in both hemispheres; and that any variations from these re- 

 sults are due to differences of temperature, topography, etc. Tlie 

 existence of these three zones of air currents, with motions as here 

 proposed, seems to furnish a full explanation of most of the facts 

 known and observed up to date. That there is a belt of calms at 

 the 80th parallel, and also a high barometer, seems to be so well 

 «stablished that no one can be found with the temerity to deny it. 

 If there be an iuterchange of air between the poles and the equator, 

 by a surface iiow southward and upper strata flowing north, as 

 proposed by Professor Ferrel and others, it seems impossible to 

 explain the existence of this calm belt and high barometric press- 

 ure at parallel 30, or at any other place between the equator and 

 the pole. The air flowing horizontally across any particular 

 locality cannot produce a calm or a high pressure at that locality, 

 VFhatever the velocity may be. A calm is produced by the meet- 

 ing or parting of winds; a high pressure is produced by a down- 

 pour, and a low pressure by an uppour of the air. 



So, also, the prevailing winds in the north temperate latitudes, 



from the south-west to the north-east, are so well established, that 



it is deemed no evidence is required here to prove their existence. 



Their direction and motion cannot be explained on Professor Fer- 



rel's theory of a southward tendency of the air in that zone at the 



surface. A calm at the pole might be reasonably deducible from 



his theory; but one at the 60th parallel is impossible. 



T. A. Bereman. 

 Mount Pleasant, la, May, 1892. 



Four- Fold Space. 



In the May 13 number of Science, I find a very interesting 

 discussion of "The Possibility of a Realization of Four Fold 

 Space," being a digest of a paper by Dr. T Proctor Hall. As I 

 have not had the pleasure of reading Dr. Hall's paper, and as I 

 have not read any fourth-dimensional literature for quite a while, 

 what I am about to say may be old. If not, and you find it wor- 

 thy of publication, you may use it. 



All modern thinkers about the Kantian philosophy of the fourth 

 dimension of space, have, I suppose, dipped more or less into 

 Professor Zollner's Transcendental Physics. It looks as if Dr. Hall 

 had done so, as his discussion of the knotted-string question and 

 the ' ' plane being " as distinguished from an ordinary three-di- 

 mensional mortal, is quite similar to certain illustrations used by 

 Professor Zollner. 



I think Dr Hall's idea of trying to get a clear concept of fourth- 

 dimensional space, by initial projections from three-dimensional 

 space, and then modifying those projections as best we can, is very 

 ingenious, and may become a very useful factor in the study of 

 the possibilities of four-dimensional space and four-dimensional be- 

 ings ; and I think he is entitled to great credit for his clear and 

 effective start made in that direction. 



I have only one criticism to make about it, which is that such 

 a process would be exceedingly slow, as slow as the building up 

 of the science of mathematics, or chemistry, or any other science 

 which had to start with wholly unknown premises. I do not 

 think that the study of four-fold space absolutely requires treat- 

 ment of this elementary character. This opinion is based upon 

 the following thoughts and inferences, which I have from time 

 to time drawn with regard to this fourth dimension, and made 

 use of in private conversation with regard thereto. 



The so-called universe of matter, as has been repeatedly said, 

 is known to us only because there is an unknown x (whether force 

 or substance we cannot tell), which successfully resists our attempts 

 to penetrate it, whether the attempt be made by the sight, the 

 touch, or such power of projectile force as we think we have suc- 

 ceeded in bringing under our control. Outside of this resistance 

 there is absolutely nothing but inference, an inference which 

 some philosophers regard as amounting to conviction, and others, 

 not. 



When we say a block of granite is impervious or impenetrable, 

 we simply announce an inference mentally drawn from impressions 

 received by our various organs; and the point which I am now 

 raising is simply this: that the same impressions might be |re- 

 ceived, and hence the same inference drawn, under a totally differ- 

 ent state of affairs, provided we assume — and we have no reason 

 for not assuming — that our standards, such as a foot of twelve 

 inches, an inch of three barley-corns, etc., are simply relative, and 

 compared with the infinite universe mean absolutely nothing, in 

 other v7ords, are not standards at all. Not to make this too long, 

 but to illustrate hurriedly where I have thought, for some years, a 

 starting point for the practical demonstration of four-dimensional 

 space may be found, let me use an illustration. 



Let us call our granite block a ten-foot cube. Standing in front 

 of it we can only see one side ; at a certain angle we can see two 

 sides. From an elevated point we can see two sides and the top; 

 but we can never see, except by the aid of reflectors, more than 

 three of the six sides at once.- We can easily walk around and 

 under it, and see the other sides. In other words, and this is the 

 key of the whole situation, we can see the whole of the cube suc- 

 cessively but never simultaneously ; and this applies to the inside 

 as well as the outside. If this granite block were magnified so 

 that each dimension was a thousand times what we have assumed 

 it to be, it might be a very porous and loosely-jointed structure ; 

 yet if our eye were placed with increased faculties at a proper dis- 

 tance, the phenomenon presented to that eye would be exactly 

 that which now shines forth in the ten-foot block of granite, and 

 our inference as to its size and structure would be identical with 

 our first assumption. 



As we have no difficulty in believing that, owing to the revolu- 

 tion of the earth combined with its motion around the sun, we 

 have been carried many miles through space in the fraction of a 

 second which elapses, as we think, between dropping a coin and 



