638 



SCIENCE. 



[N. S. Vol. I. No. 23. 



pology), Professor W. M. Flinders Petrie, 

 ofUniversity College, London; K (Botany), 

 Mr. W. T. Thiselton-Dyer, Director of the 

 Eoyal Botanic Gardens, Kew. The new 

 President will deliver his inaugural address 

 on September 11th. The two evening dis- 

 courses will be given by Professor Silvanus 

 Thompson, on ' Magnetism in Eotation,' and 

 by Professor Percj' F. Frankland, on ' The 

 Work of Pasteur and its Various Develop- 

 ments.' There will be, as usual, two soirees, 

 and also excursions to places of interest in 

 the neighiborliood of Ipswich. 



MECHANICAL INTERPRETATION OF VARIATIONS 

 OF LATITUDE. 



Under this title, in No. 345 of the Astro- 

 nomical Journal, Professor E. S. Woodward 

 seeks to deduce the law of variations of 

 latitudes from djmamical considerations. 

 Starting with the hypothesis that the earth 

 is a body of variable form, the general differ- 

 ential equations of rotation of such bodies 

 are derived by means of the Lagrangian 

 method. These equations are then shown 

 to admit of considerable simplification when 

 applied to the earth by reason of the fortu- 

 nate circumstances that the variations of 

 latitudes are very small, and that the prin- 

 cipal moments of inertia of the earth vary 

 exceedingly slowlJ^ The integrals of the 

 resulting equations give the rectangular co- 

 ordinates of the instantaneous pole of the 

 earth with respect to its pole of figure. 

 The characteristic motion of the instan- 

 taneous pole is found to be the resultant of 

 three distinct parts, namely, motion in a 

 circle about the i^ole of figure with two 

 series of elliptical motions superposed. This 

 characteristic motion is subject, neverthe- 

 less, to some fluctuations arising from vol- 

 canic and similar impulsive disturbances, as 

 well as from irregularities in meteorological 

 processes. 



The general features of latitude variations 

 thus deduced from a purely theoretical basis 



agree with those arrived at inductively by 

 Dr. Chandler in his elaborate researches. 

 Only one difficulty, in fact, seems to stand 

 now in the way of a satisfactorj^ accordance 

 of theory and observation, and that is the 

 prolongation of the period of the Eulerian 

 cj'cle from 305 to 428 days. A considerable 

 amount of space is devoted by the author to 

 a discussion of this diflicultj'. He attacks 

 the validity of the method of deriving the 

 period of that cycle from the ratio furnished 

 by precession, and concludes that the period 

 so derived ' can no longer be maintained as 

 a dogma of dj'namical astronomy.' Of 

 several causes which may modifj' this period, 

 he considers the principal one to be the tide 

 entailed by the motion of the instantaneous 

 axis of rotation about the axis of figm-e. 

 The order of magnitude of such a cause es- 

 sential to account for the discrepancj' is 

 shown to be very small. The main object of 

 the paper, however, is to obtain a correct 

 specification of the analytical form of the 

 variations in question, leaving to observa- 

 tion and subsequent investigation the de- 

 termination and reconciliation of the con- 

 stants which enter that form. 



THE MISSOURI BOTANICAL GARDEN. 



The Sixth Annual Eeport of the Mis- 

 souri Botanical Garden,* issued on Maj^ 3rd, 

 is an octavo volume of 134 pages, with 6 half- 

 tone views taken in the Garden, and 56 

 plates illustrating plants described in the 

 report. 



The report of officers of the Board of 

 Trustees shows that the receipts for the year 

 1894 were $95,555.97, and the disburse- 

 ments $75,800.69, of which $35,483.39 was 

 spent on the maintenance and improve- 

 ment of the Garden and the performance 

 and publication of scientific work; $3,692.29 

 was for banquets, exhibition premiums, a 



*3Iissouri Botanical Garden. Sixth Auuual Report. 

 St. Louis, Mo., Published by the Board of Trustees. 

 1895. 



