﻿ACADEMY 
  OF 
  SCIENCES. 
  23 
  

  

  land, 
  stretching 
  through 
  150 
  years 
  (British 
  Association 
  Report 
  for 
  1866) 
  no 
  

   such 
  maxima 
  and 
  minima 
  could 
  be 
  deduced 
  ; 
  and 
  in 
  a 
  series 
  of 
  observations 
  over 
  

   various 
  parts 
  of 
  the 
  globe, 
  gathered 
  by 
  G. 
  J. 
  Symons, 
  in 
  number 
  165 
  of 
  Nature, 
  

   the 
  .=anie 
  want 
  of 
  law 
  is 
  manifest 
  ; 
  in 
  fact, 
  where 
  maxima 
  of 
  rainfall 
  should 
  be 
  

   expected, 
  we 
  find 
  minima, 
  and 
  vice 
  versa. 
  These 
  tables 
  are, 
  however, 
  too 
  limit- 
  

   ed 
  to 
  deduce 
  a 
  general 
  law 
  therefrom. 
  The 
  materials 
  are 
  at 
  hand 
  for 
  a 
  much 
  

   more 
  comprehensive 
  treatment 
  of 
  the 
  problem. 
  

  

  But 
  if 
  there 
  is 
  a 
  law 
  in 
  such 
  cases 
  isochronous 
  with 
  the 
  exhibition 
  of 
  the 
  sun 
  

   spots, 
  it 
  must 
  be 
  qualified 
  by 
  other 
  variable 
  functions 
  than 
  rainfall 
  ; 
  such 
  as 
  the 
  

   temperature 
  and 
  pressure 
  of 
  the 
  atmosphere, 
  and 
  the 
  amount 
  of 
  aqueous 
  vapor 
  

   in 
  the 
  atmosphere, 
  the 
  direction 
  and 
  force 
  of 
  the 
  winds, 
  and 
  the 
  climatology, 
  not 
  

   only 
  of 
  the 
  adjacent 
  ocean, 
  but 
  of 
  the 
  sources 
  of 
  the 
  great 
  currents 
  that 
  cross 
  

   the 
  ocean. 
  For 
  example 
  : 
  if 
  the 
  rainfall 
  of 
  the 
  western 
  coast 
  of 
  Europe 
  is 
  as- 
  

   sumed 
  dependent 
  upon 
  the 
  same 
  causes 
  which 
  occasion 
  the 
  solar 
  spots, 
  the 
  epochs 
  

   of 
  the 
  maxima 
  and 
  minima 
  rainfall 
  would 
  not 
  coincide 
  with 
  those 
  of 
  the 
  solar 
  

   spots, 
  because 
  the 
  precipitation 
  of 
  rain 
  and 
  the 
  temperature 
  of 
  the 
  seaboards 
  of 
  

   Ireland, 
  Scotland, 
  Norway, 
  Iceland, 
  Spitzenbergen, 
  etc., 
  depend 
  upon 
  the 
  tem- 
  

   perature 
  of 
  the 
  Gulf 
  Stream 
  bathing 
  those 
  shores 
  ; 
  and 
  the 
  waters 
  of 
  the 
  Gulf 
  

   of 
  Mexico 
  heated 
  to 
  a 
  maximum 
  at 
  a 
  given 
  epoch 
  would 
  not 
  reach 
  the 
  coast 
  of 
  

   Norway 
  for 
  possibly 
  a 
  year. 
  The 
  same 
  is 
  true 
  of 
  this 
  coast 
  ; 
  the 
  heated 
  waters 
  

   of 
  the 
  great 
  Japan 
  stream, 
  at 
  their 
  point 
  of 
  departure 
  near 
  the 
  island 
  of 
  For- 
  

   mosa, 
  do 
  not 
  reach 
  this 
  coast 
  for 
  more 
  than 
  a 
  year. 
  Thus 
  whilst 
  these 
  super- 
  

   heated 
  waters 
  are 
  delayed 
  one 
  year 
  in 
  reaching 
  their 
  destinations, 
  the 
  climatic 
  

   conditions 
  of 
  the 
  coasts 
  of 
  Norway 
  and 
  of 
  California, 
  supposed 
  to 
  be 
  governed 
  

   by 
  a 
  regular 
  law. 
  have 
  been 
  changed, 
  and 
  the 
  problem 
  is 
  complicated 
  and 
  masked 
  

   by 
  these 
  changes 
  in 
  the 
  nearer 
  effects 
  of 
  the 
  climate 
  of 
  the 
  adjacent 
  continents 
  ; 
  

   and 
  in 
  the 
  European 
  case, 
  of 
  the 
  Polar 
  Basin. 
  

  

  If 
  there 
  is 
  a 
  law 
  of 
  the 
  rainfall, 
  there 
  will 
  naturally 
  be 
  a 
  similar 
  law 
  for 
  the 
  

   temperature 
  and 
  pressure 
  of 
  the 
  air, 
  and 
  for 
  the 
  winds 
  ; 
  but 
  it 
  must 
  be 
  compli- 
  

   cated 
  and 
  masked 
  by 
  the 
  influence 
  of 
  great 
  ocean 
  currents, 
  so 
  that 
  the 
  problem, 
  

   instead 
  of 
  being 
  simple 
  as 
  it 
  first 
  appears, 
  is 
  in 
  reality 
  very 
  intricate. 
  

  

  An 
  attempt 
  has 
  been 
  m 
  ide 
  to 
  give 
  an 
  eleven-year 
  period 
  to 
  the 
  cyclones 
  in 
  

   connection 
  with 
  the 
  rainfall, 
  but 
  evidently 
  upon 
  insufficient 
  data, 
  for 
  Mr. 
  Mel- 
  

   drum 
  only 
  claims 
  that 
  a 
  supposed 
  periodicity 
  has 
  been 
  made 
  out. 
  Lockyer 
  

   (Nature, 
  No, 
  163) 
  in 
  discussing 
  Mr. 
  Meldrum's 
  records 
  and 
  others 
  at 
  Madras 
  

   and 
  the 
  Cape 
  of 
  Good 
  Hope, 
  sees 
  in 
  them 
  indications 
  of 
  a 
  periodicity, 
  but 
  his 
  

   discussion 
  is 
  merely 
  tentative 
  from 
  insufficient 
  materials, 
  and 
  is 
  not 
  satisfactory. 
  

  

  The 
  same 
  eleven-year 
  period 
  has 
  been 
  assigned 
  to 
  the 
  seasons 
  of 
  great 
  freshets 
  

   in 
  California 
  ; 
  but 
  we 
  need, 
  what 
  we 
  cannot 
  obtain, 
  absolute 
  observations 
  over 
  

   extended 
  areas, 
  and 
  not 
  mere 
  reports, 
  to 
  aid 
  in 
  its 
  establishment. 
  The 
  state- 
  

   ment 
  was 
  common 
  in 
  the 
  West 
  that 
  the 
  greatest 
  freshets 
  occur 
  on 
  the 
  great 
  riv- 
  

   ers 
  of 
  the 
  Western 
  States 
  about 
  every 
  ten 
  years. 
  

  

  I 
  have 
  had 
  placed 
  in 
  graphical 
  order 
  the 
  rainfall 
  at 
  San 
  Francisco 
  for 
  twenty- 
  

   three 
  years, 
  from 
  Mr. 
  Thomas 
  Tennent's 
  observations, 
  and 
  exhibit 
  it 
  to 
  show 
  

  

  