lsi7.] 



THK CIVIL ENGINEER AND ARCHITECPS JOURNAL. 



131 



A NEW THEORY OF THE EARTH, THAT FULLY AC- 

 COUNTS FOR MANY ASTRONOMICAL, GEOGRAPHtCAL 

 AND GEOLOGICAL PHENOMENA, HITHERTO UNAC- 

 COUNTED FOR. 



By Oliver Byrne. 

 f Continued from page 101. J 



Tlie following illustration will show, in a very simple manner, how 

 different effects m.iy appear to be produced by investigating causes 

 separately, that act jointly. 



a 



j p 



Let a material point P, be acted upon by two uniform forces at the 

 same time, in the directions P A, P B, and let the lines P A, P B, re- 

 present the magnitudes of these forces. It is well known, by what 

 is technically called the parallelogram of forces, that it will not obey 

 either of these forces, but the combine J effect of both, and describe 

 the diagonal P C. Now the point P, would arrive at C, in precisely 

 the same time, if the causes of action be investigated separately, 

 even if at every alternate instant the forces alternately act; yet the 

 path described by P, would be very different from the true one, which 

 the joint actions of the two forces cause it to describe. The zigzag 

 path P, 1, 2, 3, &c., will be at best but an approximate to the true one 

 P C. This illustration of combined action, viewed jointly and sepa- 

 rately, simple as it is, compared with the joint actions of the sun, 

 moon, and the other bodies in the solar system, on the excess before 

 mentioned, shows how astronomers, by continually correcting a false 

 hypothesis, have distorted the true motion, which we shall continue 

 to explain. In stating that the earth's axis changes its position, we 

 do not consider the mass moveable with it; — no; the change of the 

 axis, which is to be understood by what is termed its rigM motion, 

 changes the position of the equator, and, therefore, the latitudes of 

 all places. It may be necessary to remark here, that the right motion 

 of the earth's axis is very slow; so much s i, that scarcely any percepti- 

 ble difference in the latitudes can be observed in 100 years, — chieflv 

 on account of this motion not being recognised in a proper manner, 

 which has tended to baffle the theory of corrections, now so dissatis- 

 factory. For the purpose of exemplification, we shall show how this 

 motion of the earth's axis would cause the phenomena of a precession 

 of the equinoxes. This may be shown by simply allowing the poles 

 to change their position in two opposite circles. It may be necessary 

 also to remark that this supposition is made merely for the purpose 

 of illustration, for the right motion of the earth's axis is not in a cir- 

 cle, but in a looped spiral curve of double curvature, the nature and 

 properties of which are given in the proposer's new work on the 

 Theory of the Heavens and Earth, before alluded to. However, when 

 this supposed plain motion is understood, the right motion o/ t/w earth's 



axis (which at once effects these apparent raotions, recognised by the 

 terms precession, nutation, and the decrease of tlie obliquity of the 



ecliptic,) can readily be conceived. If a right VmePp.he supposed 

 to revolve about its middle point O, in such a manner as to describe 

 a circle AP P" ; the other point;), will describe an equal circle, whose 

 plane will be parallel to that of the former circle. The lines P p, P"/>', 

 &c., will have the same inclination to the plane passing through O, 

 parallel to the planes of these circles. Now, if a plane be supposed 

 to pass through O, perpendicular to P;?, and intersect the plane E Be, 

 in E e, when the point P, moves to P", the plane perpendicular to 

 P" p', passing through O, will intersect the plane E' E B, in E' e' ; so 

 that if P p, P" p', &c., be considered consecutive positions of the 

 earth's axis, the plane of the ecliptic to be E B e, and the variible 

 plane pissing through O, perpendicular to P p, P" p', &c., the plane 

 of the equator, then the consecutive points E E, &c. show the pre- 

 cession of the points where the planes of the equator and ecliptic in- 

 tersect, and how their positions are changed with the motion of the 

 poles Pp. A motion similar to this, but of a more compound nature, 

 causes what is technically termed the precession of the eqinoxes. 

 Now, the spiral motion, or rather change of the earth's axis, above 

 alluded to, which is chiefly caused by the infl'jence of the sun and 

 moon on the excess of the earth above its greatest inscribed sphere, 

 is what we have designated the right motion, or change of the earth's 

 axis. The nature of this motion can be readily conceived from the 

 apparent phenomena of precession, nutation, &c. Hence, this exposi- 

 tion shows that the earth has but three motions; namely, one round 

 the sun, one on its axis, and a change of that axis ; the nature of this 

 last motion or change is something similar to that which is observed 

 in a globular body spinning on an horizontal plane. However, the 

 change of the axis in this globular body is only calculated to give an 

 idea of the uniform change of the axis of the earth, caused, as we have 

 before observed, by the constant and commanding influence of the sun 

 and moon. As the poles shift their positions on the surface, so does 

 the equator and the protuberance there; and, in fact, every particle 

 of which this globe, if we may so term it, is composed,,eudeavours to 

 accommodate itself to this motion, so that the earth's true form is 

 that which m ly not be improperly termed an exvoluted s;)heroid, 

 continually, but slowly, changing its relative position. To guard 

 against any misconception, it may be necessary to state, that the 

 change of the protuberance at the equator, or rather the change of the 

 excess of the earth above its greatest inscribed sphere, is n it a sliding 

 of that excess over the inscribed sphere, but the establishing of 

 another and another excess in different positions, in consequence of 

 the change of the position of the earth's axis, which is continually 

 being changed by the influence of the sun and moon on the excess ex- 

 isting at any time. Every particle, internal and external, natural and 

 artificial, is influenced by this motion. The sturdy edifices of man soon 

 moulder down, or their foundations are depressed or elevated : the 

 true cause is never assigned. When no local cause can be trumped up, 

 all is left upon what is commonly termed the ravages of old time, 

 which lets nothing alone. 



The changeable protuberance or excess is said to be about 34 

 miles more in diameter at the equator than the diameter through 

 the poles; — this slow and constant change of the excess of the earth 

 above its greatest inscribed sphere, has done more in baffling the ob- 

 servations of man, and all his inquiries respecting the nature and figure 

 of the earth, than any other circumstance which might be named. If 

 the earth were composed of one uniform substance, ready to accom- 

 modate itself to the behaviour of this change of protuberance, the true 

 motion of the earth's axis would have been discovered long ago. The 

 heterogeneous substances of which this planet is composed, and which 

 are more and more changed with respect to colour, pliability, and 

 form, with their varied positions by the influence of heat and cold in 

 the great laboratory of nature, must in a greater or less degree, in 

 every instance, point out the existence of this unerring law. The 

 change of this protuberance, or rather the change of all the particles 

 with respect to the imaginary line about which this planet makes its 

 daily revolutions, although very slow and gradual, effects a change in 

 the whole heterogeneous mass, every instant, more or less, according 

 to the pliability of the several parts; those parts which do not in- 

 stantly change, from the rigidness of their nature, ultimately feel its 

 sway : so that the earth would become, from what we have termed the 

 right motion of its axis, a figure whose nature and proportions could 

 be readily determined, were it composed of one yielding ami uniform 

 substance; but on account of its heterogeneousness, and ;he rigidity 

 of some of its component parts compared with others, this figure, 

 which we shall here designate an exvoluted spheroid, becomes in parts 

 more or less slightly indented or elevated, according as these parts 

 and those surrounding them are more or less sensitive of the constant 

 disturbing cause. Not only a change in the inanimate kingdoms is 

 effected by the right motion of the earth's axis, but also a constant 

 change in the animate: it is not asserting too much to say, th»t the 



