Show UNiTO U som SOT LECTURES 0 at it vyva viva ivan iva lva W n i t uni umi 4 1 salk ar ASTRONOMY r t 1 MS 1 PRATT SEN t ae 1 FT II 11 0 e earth measurement 6 of the earth Cian olan changed ged by rotation influence of the centrifuge centrifugal jab b ce cc on the weight of 4 1 1 had bodies is fin aln influence fluence of distance from 1 it J I 1 W on 03 weight in intensify cen tensely ten silv sity of gravity in different latitudes determined deterts by jend Tend pendulum pendulum exee Exve experiments tinen ts 1 A consequences h ea of J causes of he trade winds 7 weight of taw the bhole earth carth ho huja ascertained g aled density derot ay iy earth barth density of the interim interior lm cam dareol willa with the t surface C ati ogi im iii in our former lecture lectura many evIden evidences ceA ces were examined which demonstrate the ta torr movement vf of our globe its daur nal nai rotation may also alsa be proved ta exist axis t fronia iaz careful consideration of its true figure when we loosely speak of bf its figure we represent it to be a sphere a globe because it so nearly approximates to such a figure and it is only by bythe the most careful observations and measurements that we find any deviation from a sphere indeed before the dayis days of newton the earth was generally supposed to be a perfect sphere but thad that greab great philosopher demonstrated that a globe globo composed in part of fluid materials could not have a rotation upon an axis without changing its figure by ly having its polar diameter shortened and its equatorial diameter increased his calculation cu lation showed that the earth if it it rotate must be flattened in its polar regions in the shape of a turnip or an orange subsequent observations have verified his calculations cu and theory to be true and the earth is no longer in strictness considered a globe but an oblate ellipsoid or spheroid having the diameter which coincides with the axis 1300 1 shorter than the equatorial diameter it will be seen that the is so small that it does not differ much from a sphere it we held in our hand han d a wooden n model of our globe whose diameter at the equator was 15 inches the polar diameter would lack only 1 20 of an inch of being the same length a quantity so small that it could dould not possibly be detected by the eye but would require vy very nice delicate measurements to show its deviation from a globe for the purpose ot of determining the ot of the tho earth commissioners of various nations have keen been been appointed by their respective governments and furnished with the best of instruments to measure bresof arcs of the meridian in different latitudes in various parts of the earth by a comparison arlson arison of all these measurements it is found found that the length of a degree increases with the latitude being the least at the equator and ana the greatest at the poles therefore the c curvature ture tare of the earths surface must be greatest eanest at the equator and mu must 8 t adecir decrease a with the latitude and be be least i at lt the poles these merld berid lonal ional sections which pass through the poles cutting the equator at right angles are ellipses andine geometrical properties of an ellipse are such that we are enabled to assign the proportion between the lengths of its major and minor mine r axes corresponding to any proposed rate of variation in its curvature and haying determined the proportion of the two axes or diameters we can still further determine their absolute absolute lengths by knowing the length of a degree in any given latitude mr airy by a combination of 13 different arcs measured in different parts of the earcil earth has determined its and given the diameters as follows miles equatorial diameter polar rolar diameter polar compressions proportion ot of diameter as 33 to mr bessel bessei has more recently calculated the same from a combination of ten teil of the measured arcs area and his results do not daffe differ r from the diameters as given by mr airy the 1 16 part tart of a mile erom prom a comparison of the above diame tars it will be seen that the equatorial regions of our earth are about 13 miles higher highter or more dist distant tint from its contre centre than the polar this ascent from the two poles towards the equator is not sudden but gradual the elevation increasing at an average rate of about one mile in every 6 deg dega 18 minute minutes of difference of latitude or I 1 mile in in traveling from the equator to the poles there would be a rapid descent of 11 U feet per mile the gulf of mexico at the mouth of the mississippi river is sett fett higher than salt lake city and the me atlantic and pacific oceans at the equator are aro elevated more than 5 miles above our oun bar city and more than 31 miles milea above the highest peaks of the mountains which bound our valley vailey on the east the mouth of the tho mississippi river Is more than I 1 mile higher than the st louis which is situated upon uvon upolita banks some the north its mouth month is also several miles higher than the tops of the digest moun mountains t in from which intakes it takes its ita rise alse the equatorial ocean ia Is 13 miles higher than the arctic and antarctic oceans all these are phenomena arising from the form of the globe when we speak of different farent dlf dIf mountains and places being elevated above the sea level we have reference no arenc a to their relative elevations above the centre contra of the earth unless when compared with that portion of the sea which has the same latitude as the places themselves when we say our city is elevated feet above the sea level we itis so much highe bighorn above the centre contra of the earth than the equatorial or polar seas but we mean that it is s so 0 much lmh higher or more moro distant from the centre of the earth than that dortlon portion of the sea which ia is in 40 deg dog 45 minutes ef of N latitude that protuberant mass of land and water which envelopes our eur spheroid at the equator quator e is more than 21 times higher above th the poles than the highest mountains upon the earth are above the sea level perhaps some of this audience may be startled at these declarations and ready to call them in question as being contrary to their experience how it maybe may be enquired can water nin up hill or how can the great eat ocean be prevented from rushing down wn from the equator to the poles if there is an average of 11 feet fall per mile he how can an water be he kept p t from descending such a declivity we answer that it is the diurnal rotation of the earth upon its axis that preserves t the a earth in its present form and ana that maintains ns the waters in their present state of equilibrium and that causes the water of the mississippi to run up an acclivity on its ascending journey towards the equator were it not for the rotation of the eaith earth the great protuberant mass of the waters would rush down from the torrid zone with awful and tremendous force inundating the tho highest mountains in the temperate iem tem and frigid zones the foundations pf af the great deep for hundreds of miles each bach sid bid side bide 6 of the equator would be laid bare anda nd a zone of dry dryland land would appear encircling the whole earth from easu east to west connecting the equatorial portions of the eastern and western continents while heir their northern and southern portions would be overwhelmed in the midst of two great olar seas the surface of these polar seas would woula no iio longer maintain their elliptical form but would take the form of a sphere every part being equally distant from the centre centri of the earth the equatorial continent thus formed would in the lapse of bf ages be worn down b by at the h D constant action of the seas rains ax 4 and nd the worn off fragments and particles would eventually be scatter scattered dd over the bed of the oceans in the form of pebbles sand and mud which would ike like the fluid portions of the earth seek theli own lever level in tiie the deepest portions of the polar seas and in this manner the flattened portion portions O 1 of the solid spheroid would become rounded and the whole earth both S solids and fluids fiilds would assume the spherical form faim and I 1 d t thus us in the course course of millions of a ages under tinder the present laws if no rotation ex ox I 1 sted d the solid portions of our spheroid anid would become covered with i a Vh spherical ocean of uniform depth geological a facts ate said to afford abundance of evidence that the existing continents and ana islands aye kayo bayo all ball undergone changes as great lis jis as the one which we have jush just described they appear speir to haYe been more moro than thiLd onee once tern nto into fragments reduced to powder submerged pa m the great deeland de epand then thon by some ome process constructed reconstructed re handmade and made new now let us next consider the case of a perfect globe of the magnitude of our earth covered with an ocean of water of uniform depth composed of materials of uniform density or at least of a density increasing at a uniform rate from the tho surface to the cen entre treL all the blan blar particles tidies of such a globe if at test would be in a ita state teof of equilibrium bowlet such maeh a globe begin by degrees 4 to rotate upon an axis let the rotation be accelerated until it shall perform ond one revolution gutlon in as it will then have a velocity equal to the earth when this thia ro rotation commences each particle situated without the axis would have a centrifugal force or a tendency to recede from the axis in proportion to its distance from it near the poles where the centrifugal force at the surface of the globe is the weakest it acts acta at nearly right angles to the force of gravIty the under the influences of these two forces would be urged towards the equator as th the a wat water a r proceeded rodd rode eded oded upon its ita journey its distance from the axis of motion would be increase dana dand its contri centrifugal fugal force would bonse bonso consequently be more powerful though it would act at a disadvantage in consequence of its be being g more in n 0 opposition pos on to ohp central force that is for wor forming a greater greaten eater eaten angle with it than an when n near nean the poles but still the d direction action of the resultant ul t motion would be towards the equator the obtuseness of the angee angle under undo which these two forces operate would continue to td increase from th the tho e pole to the equator at ak which pido aldo the centrifugal force fonze would act zet in direct opposition to gravity and consequently the part particle particles leles would filmore fi omoro anore tendency to proceed oither either to the north or bouth south but the whole effect of sot nnie the fhe centrifugal force now would be to ronder render all bodies specifically Ug haiby harby heiby their theli ap inyard tendency from the centre centro under these those circumstance sit dit as aas apsy 0 ta o perceive that the glob globular ulai form norm ol 01 of theocian the ocean would uld liot riot any longer be the forni of I 1 libri um that the ocean surroundings t the het hot tio afo 0 poles les ies must in obedience to the 6 I 1 laws a n of mot motion loil proceed towards the e equator jual lual t 0 and nd thore there form forni a protuberance of a sufficient elevation atlon to counteract any further motion 01 of the fluid particles arising n I 1 fro from the centrifugal force of rotation the r fa form rm thus assumed by the fluid ocean would be an oblate spheroid which would be a permanent form of 0 equilibrium as long lend as the rotation continue continued uniform and it is also alio easy to conceive that solid nucleus of the earth for thou thousands sahda of miles around each pole would be lye laid bare forming two great continents while the ocean would encircle the whole earth 11 drining forming a belt or kono tono several beveral thousand miles in breadth of which the equator would be in the midst these Thes polar epolar continents as we observed concerning the equatorial continent nent would in the 1 lapsa a P of many ages become worn down an and d reduced to pebbles sand mud ac and be submerged beneath mhd ocean where under the samo same laws of force and motion which govern the fluid ele eie 1 ments it would be carried towards the equator and arrange itself in a form similar to that of the ocean with which it would be toe enveloped thus the whole earth would be covered with an ocean of nearly uniform depth and both the solid and fluid portions would be in equilibrium having a degreif degre degree of sufficient clent elent to balance the combined effects of the centripetal and centrifugal forces if by any means the rotation should be increased the would be increased the fluids upon the surface would first yield to the impulse and afterwards the solids would by bya a slower process r arrange themselves in the form of equilibrium accamo dated to the increased creased iu degree of bf rotation should the rotation be decreased down to its former velocity an equatorial ridge of mountains would be formed should an increased or bir decreased rotation take place before the time tlde fally fully to td arrange themselves in the form rm of equilibrium the consequence would be a that ridges or continents would be formea formed amed in lif different latitudes which in places laces lacos that were ol 01 a softer texture might be a worn down and submerged beneath the sea bea while those of a ii harder and more unyielding nature might still be standing above the surface of the water in the dorm of continents conti and islands we do not pretend to state slate that this is the tway that the continents and islands of our earth have received their thell present form and position but we merely state that such would be the natural tendency were the earth to receive an addition or diminution to its velocity of rotation before the solid nucleus had time to fully accommodate itself to the different forms of equilibrium corresponding to its different states of velocity whether the velocity of rotation has ever been greater or ar less loss than at the present time we have not as yet discovered any means of ascer ining tai tal ning the Tho fact that dry land and moun mountains taing do exist near the equator elevated several thoL thousand sand feet above the sea would a eem seem to ind inglette indic iette lette ato tto that the velocity of rotation has at some former period been greater than at tit present otherwise there must have been some sudden convulsion s sufficiently great to td from the bosom of the great deep the solid portions of the earth to the present elevations in those rek rei regions lons loos observation shows that thai the there has been no perceptible change in la the period of the earths rotation during the last 2000 years if our oar earth oarth were a globe when the rotation was arst first im pressed upon it its period must have been shorter or its velocity greater than it would be after having assumed the form fon for the ocean receding from the poles where the centrifugal norce force esthe is the least and proceeding to the equator where that force Is the its progress be constantly accelerated an Z an eastern direction by virtue of its increased distance from the axis of rotation the acceleration at ai farst first would not bo be sufficiently great to toa keep up with the velocity of the spherical mass over which it was passing consequently it would lag behind producing a rapid current towards the west which combined with the guir current rent nent proceeding towards the equator would in tha northern hemisphere incline it to the southwest and hi in the southern hemisphere towards the northwest these currents acting upon the spherical form of the earth over which |