D RA Y S O N I A BEI N G AN ATTEMPT TO EXPLAIN AN D POPULARISE THE SY STEM OF THE SECON D ROTATI ON OF THE EARTH AS DISCOVERED BY THE LATE MA"OR- EN L DRAY SON G ERA A . W . FOR FI FTEEN Y E ARS PROFESSOR RO YAL MI LI TARY ACADE MY WOOLWI CH , ALSO GIV IN G THE PROBAB LE DATE AN D DURATION OF THE LAST ’ GLAC A L ER OD AN D FURN S NG GEN ERAL DRAY SON S DATA I P I , I HI , FROM WHICH AN Y PERSON OF ORD IN ARY MATHE MATICAL AB ILITY I s EN AB LED TO CALCULATE THE OB L U T OF THE ECL TI C IQ I Y IP , THE RECESS ON OF THE E U N OXES AN D THE R T P I Q I , IGH ASCEN SION AN D D ECLIN ATION OF THE FIXED STARS FOR AN Y YEA AST RESENT OR UTURE R, P , P , F DE O EY ADMIRAL SIR ALGERNON F. R H RS ' K . C . B E L O N G M A N S R E N A 0 0 . , G N D R 39 PA TERN OSTE ROW, LON DON N EW YORK BOMBAY AN D CALCUTTA , , P R E F A C E IN the following treatise I have adopted the title Dray sonia in honour of a man whose scien tific attainments have but been little known or recognised, whose death in September 1901 was r o to r mi l c a g eat l ss ast ono ca scien e, and who in u u s l he i f t re day wil , I think, acknowledged as hav ng been a - remarkable discoverer . I refer to the late Major General Al W r R Ar fred ilks D ayson, late oyal tillery, who, i i ui hi s in add tion to d sting s ng him elf in his profession, was for fi t P s R M A W w f een years rofe sor, oyal ilitary cademy, ool ich, and for two years attached to the Royal Observatory at ' G u Practi al Mtlztar Sur ve in The reenwich, a thor of c y y g, Conmwn Si hts in the Heavens The Last Glacial E och E g , p , w er'iences o a Woolwich Professor Thirt Thousand ears p f , y Y of ’ Earth s Past Histor r the y, ead by the aid of the discovery of o Untrodden Ground I m o the sec nd rotation of the earth, , p rtant Geolo ists Pro er Motton o the Fixed Stars and g , p f , etc. ull diffi u I am f y aware of the c lty of my task, and of how imperfectly I can do ju stice to Drayson in attempting to e d ul describe his syst m indee , I sho d not venture the attempt not G n r s his were it that e e al Dray on, shortly before death, u u u repeatedly rged me to write pon the s bject . Writing to me very shortly before his death, he said The reason why I thought that you ought to write something is that it would be a loss to astronomical science if the accurate calculations which you have made were allowed to be buried in your work book and among my papers . I refer especially to your PREFACE 20 - 0529 investigations to obtain the annu al motion of the pole , u C e r A . D . 229475 the ann al angle at . the zero y a , u ui the cycle years, the ann al precession of the eq nox 1 00 u u i u in 9 , the ann al dimin tion of the obl q ity and the variable rate of this decrease . ’ All these calculations are based on soun d geometry. In hi s again urging me in his last touching letter before death, when complaining bitterly of the unr easoning opposition he S an d had encoun tered, he said I have pent between two u hl . three hundred po nds in getting my books , pamp ets , etc , u i un s ur . p bl shed, and have received less than ten po d in ret n - but ru Money making has not been my object, that t ths in nature should be made known . I can only claim to have u ul done my best, tho gh whether good res ts will follow I ’ cannot say. I also can only claim to have done my best. My work in assistin g Drayson began after reading his o n Ground Untr dde , and has been carried on almost entirely ’ Dra son s u hr by letter . y letters to me amo nted to t ee or u d un his . four hundred, and were contin e til death From ’ this correspondence and from Drayson s works I learned a u u li — great deal, and fo nd the occ pation enthral ng too much ’ k Shortrede s mir ms so, for in wor ing with ad able logarith , l which admit of accuracy to the fi of a second of arc and to "fi m u ur i of a second of time, p and into the small ho s of the n ght, n I considerably impaired my eyesight. I was i du ced to look ’ Dra son s h into y system by my old and distinguis ed friend, n C u the late Sir Joh owell, who , when on d ty at Osborne, had ’ ra son s ro n o E . lent D y Unt dde Gr und to H. H the then Crown Pr G fte ds E ss incess of ermany, a rwar the mpre Frederick, and H . R . H. told me how great an interest had taken in the matter . u H. R The s bject also has engaged the attention of . H. the u C u W A D ke of onna ght, who, when at oolwich cademy as a u u cadet, had st died nder Drayson, and was thus aware of i his great abil ty. I mention this as another instance of the PREFACE great interest always taken by members of our Royal Family fi in scienti c matters . ’ l sc Dra son s u I be ieve I have been a good holar of y , j dging ki ff from his nd appreciation of my e orts , for in an article of hi s orkshire Post some years ago in the Y , the following com mendation appears It is quite un necessary for me to refer fi m to the scienti c attain ents , especially in practical astro R N A mi . nomy, possessed by d ral de Horsey In the oyal avy n ur these are well k own . I may say, however , that d ing the fifteen years that I was Professor of Woolwich I looked over several thousand examination papers on various qu estions in practical astronomy whi ch had been worked out by officers and cadets , who were excellent mathematicians , and to whom the practical working of spherical trigonometry was mere ’ but child s play, in no single instance have I seen anything equal in accuracy and neatness to the work accomplished by ’ Admiral de Horsey. The above flattering opinion of my attainments far exceed u but s ch abilities as I may possess, I here insert it as a record ’ of General Drayson s appreciation Of the assistance I rendered him in astronomi cal compu tations from 1893 u ntil that dis ’ ’ 01 Dra son s tingui shed astronomer s death in 19 . y lamented death occurred withou t his receiving that pu blic recognition fi m di hi of his scienti c attain ents and scoveries w ch he merited, and which I trust posterity will accord him . DE O EY . F. R . H R A. S 1 Gowns, Mar ch 191 . C O N T E N T S PREFACE ’ DRAY SON S THEORY OF THE SECON D ROTA TION OF THE POLE OF THE EARTH ZERO YEAR STAN DARD OF Trn E AND RIGHT ASCENSION ’ ‘ TEMPERATE GLACIAL EPOCHS I N TR O D U C T I O N DRAYSON’S SECOND ROTATION OF THE EARTH ' ’ E ur s mu o — t. v L L p e. GA I EO A . D. t I N the above diagram the circle is intended to represent the path traced by the pole of the earth in its course round a ° ’ " d u 29 25 47 f C cycle of years with a ra i s of rom , the E centre of second rotation . is the pole of the ecliptic distant ° Z u 6 f 0. abo t rom , which I have termed the zero year, is A D 2295 E the position the pole will attain in . when and C are aligned ; when the obliquity of the ecliptic will be at its mi i um m dl n m , and the earth therefore at the id e point of Z’ its temperate epoch . represents the place the pole at tained G E B C at the middle of the last lacial poch, . , ° ’ when the obliquity of the ecliptic was abou t 35 25 P the r u PE represents the pole of ea th at vario s periods , l u i u Pa the ob iq ity of the ecliptic at var o s times, the polar ’ di a OPa stance of (say) Draconis , and the angle the right Ca i o ascension of that star, and its d stance from the pole f A 2 i P i second rotation .