﻿1875.] 
  

  

  On 
  certain 
  Alloys 
  of 
  Silver 
  and 
  Copper. 
  

  

  481 
  

  

  Nares 
  (Capt.), 
  F.E.S. 
  Eeports 
  on 
  Ocean 
  Soundings 
  and 
  Temperature, 
  

   New 
  Zealand 
  to 
  Torres 
  Strait, 
  Torres 
  Strait 
  to 
  Manila 
  and 
  Hong 
  

   Kong. 
  H.M.S. 
  ' 
  Challenger.' 
  No. 
  3. 
  folio. 
  London 
  1875. 
  

  

  The 
  Admiralty. 
  

  

  Eeuschle 
  (C. 
  G.) 
  Tafeln 
  complexer 
  Primzahlen 
  welche 
  aus 
  Wurzeln 
  

   der 
  Einheit 
  gebildet 
  sind. 
  4to. 
  Berlin 
  1875. 
  The 
  Author. 
  

  

  Eosenbusch 
  (H.) 
  Mikroskopische 
  Physiographie 
  der 
  petrographisch 
  

   wichtigen 
  Mineralien. 
  8vo. 
  Stuttgart 
  1873. 
  C. 
  Darwin, 
  F.E.S. 
  

  

  Siemens 
  (C. 
  W.), 
  F.E.S. 
  Electrical-Eesistance 
  Thermometer 
  and 
  Pyro- 
  

   meter. 
  8vo. 
  London 
  1875. 
  The 
  Author. 
  

  

  Warren 
  (Gr. 
  K.) 
  An 
  Essay 
  concerning 
  important 
  physical 
  features 
  

   exhibited 
  in 
  the 
  Valley 
  of 
  the 
  Minnesota 
  Eiver. 
  8vo. 
  Washington 
  

  

  Eough 
  Notes 
  of 
  Journeys 
  made 
  in 
  the 
  years 
  1868-73 
  in 
  Syria, 
  India, 
  

  

  u 
  On 
  the 
  Liquation, 
  Fusibility, 
  and 
  Density 
  of 
  certain 
  Alloys 
  

   of 
  Silver 
  and 
  Copper." 
  By 
  W. 
  Chandler 
  Roberts, 
  Chemist 
  

   of 
  the 
  Mint. 
  Communicated 
  by 
  Dr. 
  Percy, 
  F.E.S. 
  Received 
  

   March 
  11, 
  1875*. 
  

  

  Alloys 
  of 
  silver 
  and 
  copper 
  possess 
  many 
  curious 
  chemical 
  and 
  physical 
  

   properties 
  which 
  make 
  them 
  interesting 
  apart 
  from 
  their 
  economic 
  value, 
  

   and 
  entitle 
  them 
  to 
  careful 
  investigation. 
  The 
  most 
  remarkable 
  of 
  these 
  

   is 
  a 
  molecular 
  mobility, 
  in 
  virtue 
  of 
  which 
  certain 
  combinations 
  of 
  the 
  

   constituents 
  of 
  a 
  molten 
  alloy 
  become 
  segregated 
  from 
  the 
  mass, 
  the 
  

   homogeneous 
  character 
  of 
  which 
  is 
  thereby 
  destroyed. 
  

  

  These 
  irregularities 
  of 
  composition 
  have 
  long 
  been 
  known. 
  Some 
  

   observations 
  of 
  Lazarus 
  Erckern, 
  in 
  a 
  work 
  published 
  in 
  the 
  seventeenth 
  

   century 
  t, 
  show 
  that 
  he 
  was 
  familiar 
  with 
  them; 
  that 
  Jars 
  possessed 
  

   more 
  accurate 
  information 
  on 
  the 
  subject 
  is 
  proved 
  by 
  his 
  stating 
  

   explicitly, 
  in 
  a 
  memoir 
  published 
  in 
  1781 
  1, 
  that 
  in 
  ingots 
  of 
  silver-copper 
  

   alloys 
  containing 
  much 
  of 
  the 
  base 
  metal, 
  the 
  centre 
  of 
  the 
  mass 
  is 
  less 
  

   rich 
  than 
  the 
  external 
  portions. 
  

  

  * 
  Eead 
  March 
  18, 
  1875. 
  See 
  ante, 
  p. 
  349. 
  

  

  t 
  His 
  work 
  was 
  translated 
  in 
  1686 
  by 
  Sir 
  John 
  Pettus. 
  See 
  'Fleta 
  Minor,' 
  

   Book 
  I. 
  p. 
  62. 
  

  

  | 
  Voyages 
  Metallurgiques, 
  t. 
  iii. 
  p. 
  270. 
  

  

  1874. 
  

  

  The 
  Author. 
  

  

  Japan, 
  &c. 
  8vo. 
  London 
  1875. 
  

  

  Messrs. 
  Triibner. 
  

  

  2 
  p 
  2 
  

  

  