THE 
LONDON,  EDINBURGH,  and  DUBLIN 
Ml 
PHILOSOPHICAL  MAGAZINE 
AND 
JOURNAL  OF   SCIENCE. 
CONDUCTED  BY 
SIR  ROBERT  KANE,  LL.D.  F.R.S.  M.R.I.A.  F.C.S. 
SIR  WILLIAM  THOMSON,  Knt.  LL.D.  F.R.S.  &c. 
AND 
WILLIAM  FRANCIS,  Ph.D.  F.L.S.  F.R.A.S.  F.C.S. 
'•  Nee  aranearum  sane  textus  ideo  melior  quia  ex  se  fila  gignunt,  nee  noster 
vilior  quia  ex  alienis  libamus  ut  apes."    Just.  Lips.  Polit.  lib.  i.  cap.  1 .  Not. 
VOL.  XLIII.— FOURTH  SERIES. 
JANUARY— JUNE  1872. 
LONDON. 
TAYLOR  AND  FRANCIS,  RED  LION  COURT,  FLEET  STREET, 
Printers  and  Publishers  to  the  University  of  London  ; 
SOLD  BY  LONGMANS,  GREEN,  READER.  AND  DYER  ',    KENT  AND  CO.  J    SIMPKIN,  MARSHALL, 
KJTD  CO.  ;    AND  WIIITTAKER  AND  CO.  ; — AND  BY  ADAH  AND  CHARLES  BLACK, 
AND  THOMAS  CLARK,    EDINBURGH;    SMITH  AND  SON,  GLASGOW. — 
HODGES,    FOSTER,    AND    CO,    DUBLIN: — PUTNAM,    NEW 
YORK: — AND    ASHER    AND    CO.,    BERLIN. 
