THE EARTH J,H.POINTING The Manuals of Science andCambridge Literature THE EARTH ITS AND SPINWEIGHTSHAPE, SIZE, CAMBRIDGE UNIVERSITY PRESS FETTER E.C.LANE, C. F. MANAGERCLAY, STREET : PRINCES(EUtnburgf) 100, W.C.fLotrtott: H. K. GOWER STREET,LEWIS, 136, STRANDWILLIAM WESLEY & SON, ESSEX28, Berlin: A. ASHER AND CO. F. A. BROCKHAUSletpjifl: P. PUTNAM'S SONStfo lorfc: G. MACMfLLAN AND LTD.JSotnbae anto Calcutta: CO., All reserved rights THE EARTH ITS WEIGHTSHAPE, SIZE, AND SPIN H. J. POYNTING, F.R.S. Sc.D., Late Fellow of College,Trinity Mason ProfessorCambridge ; of in the Physics University of Birmingham :Cambridge at the Press University New York: G. P. Putnam's Sons 1913 PRINTED I5Y M.A.JOHN CLAY, AT PRESSTHE UNIVERSITY With the the coat arms r.tof ofexception the the on the title is a foot, design page one used the earliest known reproduction of by JohnCambridge printer, Siberch, 1521 PREFACE FT!HE aim of this book is to in aexplain general -*- without how themathematicalway, detail, and size of the P]arth have been determined,shape how its mass has been and how we knowmeasured, that it and so that it is arotates, uniformly nearly Some account is of thetime-keeper. givenperfect tidal action which must be thegradually reducing a of which our is duespin, subject knowledge chiefly to researches of Darwin.