e；　or　the　particles　of　the　two　substances　would　be　most　favourably　situated　for　the　action　of　caloric；　electricity；　or　other　causes；　to　produce　the　combination。　　It　would　indeed　seem　to　follow；　that　if　combination　should　take　place　under　such　circumstances；　then　the　most　probable　proportion　in　which　the　atoms　would　unite；　should　be　that　which　furnished　a　fluid　of　the　least　specific　gravity：　　but　until　the　experiments　are　made；　it　is　by　no　means　certain　that　other　combinations　might　not　be　produced。＇
  The　singular　minuteness　of　the　particles　of　bodies　submitted　by　Dr。　Wollaston　to　chemical　analysis；　has　excited　the　admiration　of　all　those　who　have　had　the　good　fortune　to　witness　his　experiments；　and　the　methods　he　employed　deserve　to　be　much　more　widely　known。
  It　appears　to　me　that　a　great　mistake　exists　on　the　subject。　　It　has　been　adduced　as　one　of　those　facts　which　prove　the　extraordinary　acuteness　of　the　bodily　senses　of　the　individual；　a　circumstance　which；　if　it　were　true；　would　add　but　little　to　his　philosophical　character；　I　am；　however；　inclined　to　view　it　in　a　far　different　light；　and　to　see　in　it　one　of　the　natural　results　of　the　admirable　precision　of　his　knowledge。
  During　the　many　opportunities　I　have　enjoyed　of　seeing　his　minute　experiments；　I　remember　but　one　instance　in　which　I　noticed　any　remarkable　difference　in　the　acuteness　of　his　bodily　faculties；　either　of　his　hearing；　his　sight；　or　of　his　sense　of　smell；　from　those　of　other　persons　who　possessed　them　in　a　good　degree。　＇This　was　at　Mr。　South's　observatory；　and　the　object　was；　the　dots　on　the　declination　circle　of　his　equatorial；　but；　in　this　instance；　Dr。　Wollaston　did　not　attempt　to　TEACH　ME　HOW　TO　SEE　THEM。＇
  He　never　showed　me　an　almost　microscopic　wire；　which　was　visible　to　his；　and　invisible　to　my　own　eye：　　even　in　the　beautiful　experiments　he　made　relative　to　sounds　inaudible　to　certain　ears；　he　never　produced　a　tone　which　was　unheard　by　mine；　although　sensible　to　his　ear；　and　I　believe　this　will　be　found　to　have　been　the　case　by　most　of　those　whose　minds　had　been　much　accustomed　to　experimental　inquiries；　and　who　possessed　their　faculties　unimpaired　by　illness　or　by　age。
  It　was　a　much　more　valuable　property　on　which　the　success　of　such　inquiries　depended。　　It　arose　from　the　perfect　attention　which　he　could　command；　and　the　minute　precision　with　which　he　examined　every　object。　　A　striking　illustration　of　the　fact　that　an　object　is　frequently　not　seen；　FROM　NOT　KNOWING　HOW　TO　SEE　IT；　rather　than　from　any　defect　in　the　organ　of　vision；　occurred　to　me　some　years　since；　when　on　a　visit　at　Slough。　　Conversing　with　Mr。　Herschel　on　the　dark　lines　seen　in　the　solar　spectrum　by　Fraunhofer；　he　inquired　whether　I　had　seen　them；　and　on　my　replying　in　the　negative；　and　expressing　a　great　desire　to　see　them；　he　mentioned　the　extreme　difficulty　he　had　had；　even　with　Fraunhofer's　description　in　his　hand　and　the　long　time　which　it　had　cost　him　in　detecting　them。　　My　friend　then　added；　〃I　will　prepare　the　apparatus；　and　put　you　in　such　a　position　that　they　shall　be　visible；　and　yet　you　shall　look　for　them　and　not　find　them：　　after　which；　while　you　remain　in　the　same　position；　I　will　instruct　you　how　to　see　them；　and　you　shall　see　them；　and　not　merely　wonder　you　did　not　see　them　before；　but　you　shall　find　it　impossible　to　look　at　the　spectrum　without　seeing　them。〃
  On　looking　as　I　was　directed；　notwithstanding　the　previous　warning；　I　did　not　see　them；　and　after　some　time　I　inquired　how　they　might　be　seen；　when　the　prediction　of　Mr。　Herschel　was　completely　fulfilled。
  It　was　this　attention　to　minute　phenomena　which　Dr。　Wollaston　applied　with　such　powerful　effect　to　chemistry。　　In　the　ordinary　cases　of　precipitation　the　cloudiness　is　visible　in　a　single　drop　as　well　as　in　a　gallon　of　a　solution；　and　in　those　cases　where　the　cloudiness　is　so　slight；　as　to　require　a　mass　of　fluid　to　render　it　visible；　previous　evaporation；　quickly　performed　on　slips　of　window　glass；　rendered　the　solution　more　concentrated。
  The　true　value　of　this　minute　chemistry　arises　from　its　cheapness　and　the　extreme　rapidity　with　which　it　can　be　accomplished：　　it　may；　in　hands　like　those　of　Wollaston；　be　used　for　discovery；　but　not　for　measure。　　I　have　thought　it　more　necessary　to　place　this　subject　on　what　I　consider　its　true　grounds；　for　two　reasons。　　In　the　first　place；　I　feel　that　injustice　has　been　done　to　a　distinguished　philosopher　in　attributing　to　some　of　his　bodily　senses　that　excellence　which　I　think　is　proved　to　have　depended　on　the　admirable　training　of　his　intellectual　faculties。　　And；　in　the　next　place；　if　I　have　established　the　fact；　whilst　it　affords　us　better　means　of　judging　of　such　observations　as　lay　claim　to　an　accuracy　〃MORE　THAN　HUMAN；〃　it　also　opens；　to　the　patient　inquirer　into　truth；　a　path　by　which　he　may　acquire　powers　that　he　would　otherwise　have　thought　were　only　the　gift　of　nature　to　a　favoured　few。
  APPENDIX；　No。　1。
  In　presenting　to　my　readers　the　account　of　the　meeting　of　men　of　science　at　Berlin；　in　the　autumn　of　1828；　I　am　happy　to　be　able　to　state；　that　its　influence　has　been　most　beneficial；　and　that　the　annual　meeting　to　be　held　in　1831；　will　take　place　at　Vienna；　the　Emperor　of　Austria　having　expressed　a　wish　that　every　facility　which　his　capital　affords　should　be　given　to　promote　its　objects。
  It　is　gratifying　to　find　that　a　country；　which　has　hitherto　been　considered　adverse　to　the　progress　of　knowledge；　should　become　convinced　of　its　value；　and　it　is　sincerely　to　be　hoped；　that　every　one　of　the　numerous　members　of　the　Society　will　show；　by　his　conduct；　that　the　paths　of　science　are　less　likely　than　any　others　to　interfere　with　those　of　politics。
  ACCOUNT　OF　THE　GREAT　CONGRESS　OF　PHILOSOPHERS　AT　BERLIN；　ON　THE　18TH　OF　SEPTEMBER　1828。　　FROM　THE　EDINBURGH　JOURNAL　OF　SCIENCE；　APRIL；　1829。
  The　existence　of　a　large　society　of　cultivators　of　the　natural　sciences　meeting　annually　at　some　great　capital；　or　some　central　town　of　Europe；　is　a　circumstance　almost　unknown　to　us；　and　deserving　of　our　attention；　from　the　important　advantages　which　may　arise　from　it。
  About　eight　years　ago；　Dr。　Okens；　of　Munich；　suggested　a　plan　for　an　annual　meeting　of　all　Germans　who　cultivated　the　sciences　of　medicine　and　botany。　　The　first　meeting；　of　about　forty　members；　took　place　at　Leipsic；　in　1822；　and　it　was　successively　held　at　Halle；　Wurtzburg；　Frankfort　on　the　Maine；　Dresden；　Munich；　and　Berlin。　All　those　who　had　printed　a　certain　number　of　sheets　of　their　inquiries　on　these　subjects　were　considered　members　of　this　academy。
  The　great　advantages　which　resulted　to　these　sciences　from　the　communication　of　observations　from　all　quarters　of　Germany；　soon　induced　an　extension　of　the　plan；　and　other　departments　of　natural　knowledge　were　admitted；　until；　at　the　last　meeting；　the　cultivators　even　of　pure　mathematics　were　found　amongst　the　ranks　of　this　academy。
  Several　circumstances；　independent　of　the　form　and　constitution　of　the　academy；　contributed　to　give　unwonted　splendour　to　the　last　meeting；　which　took　place　at　Berlin　in　the　middle　of　September　of　the　last　year。
  The　capital　selected　for　its　temporary　residence　is　scarcely　surpassed　by　any　in　Europe　in　the　number　and　celebrity　of　its　savans。
  The　taste　for　knowledge　possessed　by　the　reigning　family；　has　made　knowledge　itself　fashionable；　and　the　severe　sufferings　of　the　Prussians　previous　to　the　war；　by　which　themselves　and　Europe　were　freed；　have　impressed　on　them　so　strongly　the　lesson　that　〃knowledge　is　power；〃　that　its　effects　are　visible　in　every　department　of　the　government；　and　there　is　no　country　in　Europe　in　which　talents　and　genius　so　surely　open　for　their　possessors　the　road　to　wealth　and　distinction。
  Another　circumstance　also　contributed　its　portion　to　increase　the　numbers　of　the　meeting　of　the　past　year。　　The　office　of　president；　which　is　annually　changed；　was　assigned　to　M。　Alexander　de　Humboldt。　　The　universality　of　his　acquirements；　which　have　left　no　branch　within　the　wide　range　of　science　indifferent　or　unexplored；　has　connected　him　by　friendship　with　almost　all　the　most　celebrated　philosophers　of　the　age；　whilst　the　polished　amenity　of　his　manners；　and　that　intense　desire　of　acquiring　and　of　spreading　knowledge；　which　so　peculiarly　characterizes　his　mind；　renders　him　accessible　to　all　strangers；　and　insures　for　them　the　assistance　of　his　counsel　in　their　scientific　pursuits；　and　the　advantage　of　being　made　known　to　all　those　who　are　interested　or　occupied　in　similar　inquiries。
  Professor　Lichtenstein；　（Director　of　the　Museum　of　Zoology；）　as　secretary　of　the　academy；　was　indefatigable　in　his　attentions；　and　most　ably　seconded　the　wishes　of　its　distinguished　president。
  These　two　gentlemen；　assisted　by　several　of　the　residents　at　Berlin；　undertook　the　numerous　preliminary　arrangements　necessary　for　the　accommodation　of　the　meeting。
  On　the　18th　of　September；　1828；　there　were　assembled　at　Berlin　377　members　of　the　academy；　whose　names　and　residences　（in　Berlin）　were　printed　in　a　small　pamphlet；　and　to　each　name　was　attached　a　number；　to　indicate　his　seat　in　the　great　concert　room；　in　which　the　morning　meetings　took　place。　　Each　member　was　also　provided　with　an　engraved　c