。　　There　are　other　advantages　which　are　perhaps　of　more　importance　to　the　public。　The　numbers　which　compose　the　learned　professions　in　England　are　so　considerable；　that　a　kind　of　public　opinion　is　generated　amongst　them；　which　powerfully　tends　to　repress　conduct　that　is　injurious　either　to　the　profession　or　to　the　public。　　Again；　the　mutual　jealousy　and　rivalry　excited　amongst　the　whole　body　is　so　considerable；　that　although　the　rank　and　estimation　which　an　individual　holds　in　the　profession　may　be　most　unfairly　appreciated；　by　taking　the　opinion　of　his　rival；　yet　few　estimations　will　be　found　generally　more　correct　than　the　opinion　of　a　whole　profession　on　the　merits　of　any　one　of　its　body。　　This　test　is　of　great　value　to　the　public；　and　becomes　the　more　so；　in　proportion　to　the　difficulty　of　the　study　to　which　the　profession　is　devoted。　　It　is　by　availing　themselves　of　it　that　men　of　sense　and　judgment；　who　have　occasion　for　the　services　of　professional　persons；　are；　in　a　great　measure；　guided　in　their　choice。
  The　pursuit　of　science　does　not；　in　England；　constitute　a　distinct　profession；　as　it　does　in　many　other　countries。　　It　is　therefore；　on　that　ground　alone；　deprived　of　many　of　the　advantages　which　attach　to　professions。　　One　of　its　greatest　misfortunes　arises　from　this　circumstance；　for　the　subjects　on　which　it　is　conversant　are　so　difficult；　and　require　such　unremitted　devotion　of　time；　that　few　who　have　not　spent　years　in　their　study　can　judge　of　the　relative　knowledge　of　those　who　pursue　them。　　It　follows；　therefore；　that　the　public；　and　even　that　men　of　sound　sense　and　discernment；　can　scarcely　find　means　to　distinguish　between　the　possessors　of　knowledge；　in　the　present　day；　merely　elementary；　and　those　whose　acquirements　are　of　the　highest　order。　　This　remark　applies　with　peculiar　force　to　all　the　more　difficult　applications　of　mathematics；　and　the　fact　is　calculated　to　check　the　energies　of　those　who　only　look　to　reputation　in　England。
  As　there　exists　with　us　no　peculiar　class　professedly　devoted　to　science；　it　frequently　happens　that　when　a　situation；　requiring　for　the　proper　fulfilment　of　its　duties　considerable　scientific　attainments；　is　vacant；　it　becomes　necessary　to　select　from　among　amateurs；　or　rather　from　among　persons　whose　chief　attention　has　been　bestowed　on　other　subjects；　and　to　whom　science　has　been　only　an　occasional　pursuit。　　A　certain　quantity　of　scientific　knowledge　is　of　course　possessed　by　individuals　in　many　professions；　and　when　added　to　the　professional　acquirements　of　the　army；　the　navy；　or　to　the　knowledge　of　the　merchant；　is　highly　meritorious：　　but　it　is　obvious　that　this　may　become；　when　separated　from　the　profession；　quite　insignificant　as　the　basis　of　a　scientific　reputation。
  To　those　who　have　chosen　the　profession　of　medicine；　a　knowledge　of　chemistry；　and　of　some　branches　of　natural　history；　and；　indeed；　of　several　other　departments　of　science；　affords　useful　assistance。　　Some　of　the　most　valuable　names　which　adorn　the　history　of　English　science　have　been　connected　with　this　profession。
  The　causes　which　induce　the　selection　of　the　clerical　profession　are　not　often　connected　with　science；　and　it　is；　perhaps；　a　question　of　considerable　doubt　whether　it　is　desirable　to　hold　out　to　its　members　hopes　of　advancement　from　such　acquirements。　As　a　source　of　recreation；　nothing　can　be　more　fit　to　occupy　the　attention　of　a　divine；　and　our　church　may　boast；　in　the　present　as　in　past　times；　that　the　domain　of　science　has　been　extended　by　some　of　its　brightest　ornaments。
  In　England；　the　profession　of　the　law　is　that　which　seems　to　hold　out　the　strongest　attraction　to　talent；　from　the　circumstance；　that　in　it　ability；　coupled　with　exertion；　even　though　unaided　by　patronage；　cannot　fail　of　obtaining　reward。　　It　is　frequently　chosen　as　an　introduction　to　public　life。　　It　also　presents　great　advantages；　from　its　being　a　qualification　for　many　situations　more　or　less　remotely　connected　with　it；　as　well　as　from　the　circumstance　that　several　of　the　highest　officers　of　the　state　must　necessarily　have　sprung　from　its　ranks。
  A　powerful　attraction　exists；　therefore；　to　the　promotion　of　a　study　and　of　duties　of　all　others　engrossing　the　time　most　completely；　and　which　is　less　benefited　than　most　others　by　any　acquaintance　with　science。　　This　is　one　amongst　the　causes　why　it　so　very　rarely　happens　that　men　in　public　situations　are　at　all　conversant　even　with　the　commonest　branches　of　scientific　knowledge；　and　why　scarcely　an　instance　can　be　cited　of　such　persons　acquiring　a　reputation　by　any　discoveries　of　their　own。
  But；　however　consistent　other　sciences　may　be　with　professional　avocations；　there　is　one　which；　from　its　extreme　difficulty；　and　the　overwhelming　attention　which　it　demands；　can　only　be　pursued　with　success　by　those　whose　leisure　is　undisturbed　by　other　claims。　　To　be　well　acquainted　with　the　present　state　of　mathematics；　is　no　easy　task；　but　to　add　to　the　powers　which　that　science　possesses；　is　likely　to　be　the　lot　of　but　few　English　philosophers。
  SECTION　2。
  OF　NATIONAL　ENCOURAGEMENT。
  The　little　encouragement　which　at　all　previous　periods　has　been　afforded　by　the　English　Government　to　the　authors　of　useful　discoveries；　or　of　new　and　valuable　inventions；　is　justified　on　the　following　grounds：
  1。　　The　public；　who　consume　the　new　commodity　or　profit　by　the　new　invention；　are　much　better　judges　of　its　merit　than　the　government　can　be。
  2。　　The　reward　which　arises　from　the　sale　of　the　commodity　is　usually　much　larger　than　that　which　government　would　be　justified　in　bestowing；　　and　it　is　exactly　proportioned　to　the　consumption；　that　is；　to　the　want　which　the　public　feel　for　the　new　article。
  It　must　be　admitted　that；　as　general　principles；　these　are　correct：　　there　are；　however；　exceptions　which　flow　necessarily　from　the　very　reasoning　from　which　they　were　deduced。　　Without　entering　minutely　into　these　exceptions；　it　will　be　sufficient　to　show　that　all　abstract　truth　is　entirely　excluded　from　reward　under　this　system。　　It　is　only　the　application　of　principles　to　common　life　which　can　be　thus　rewarded。　　A　few　instances　may　perhaps　render　this　position　more　evident。　　The　principle　of　the　hydrostatic　paradox　was　known　as　a　speculative　truth　in　the　time　of　Stevinus；　＇About　the　year　1600＇　and　its　application　to　raising　heavy　weights　has　long　been　stated　in　elementary　treatises　on　natural　philosophy；　as　well　as　constantly　exhibited　in　lectures。　Yet；　it　may　fairly　be　regarded　as　a　mere　abstract　principle；　until　the　late　Mr。　Bramah；　by　substituting　a　pump　instead　of　the　smaller　column；　converted　it　into　a　most　valuable　and　powerful　engine。The　principle　of　the　convertibility　of　the　centres　of　oscillation　and　suspension　in　the　pendulum；　discovered　by　Huygens　more　than　a　century　and　a　half　ago；　remained；　until　within　these　few　years；　a　sterile；　though　most　elegant　proposition；　when；　after　being　hinted　at　by　Prony；　and　distinctly　pointed　out　by　Bonenberger；　it　was　employed　by　Captain　Kater　as　the　foundation　of　a　most　convenient　practical　method　of　determining　the　length　of　the　pendulum。The　interval　which　separated　the　discovery；　by　Dr。　Black；　of　latent　heat；　from　the　beautiful　and　successful　application　of　it　to　the　steam　engine；　was　comparatively　short；　but　it　required　the　efforts　of　two　minds；　and　both　were　of　the　highest　order。The　influence　of　electricity　in　producing　decompositions；　although　of　inestimable　value　as　an　instrument　of　discovery　in　chemical　inquiries；　can　hardly　be　said　to　have　been　applied　to　the　practical　purposes　of　life；　until　the　same　powerful　genius　which　detected　the　principle；　applied　it；　by　a　singular　felicity　of　reasoning；　to　arrest　the　corrosion　of　the　copper…sheathing　of　vessels。　　That　admirably　connected　chain　of　reasoning；　the　truth　of　which　is　confirmed　by　its　very　failure　as　a　remedy；　will　probably　at　some　future　day　supply；　by　its　successful　application；　a　new　proof　of　the　position　we　are　endeavouring　to　establish。
  ＇I　am　authorised　in　stating；　that　this　was　regarded　by　Laplace　as　the　greatest　of　Sir　Humphry　Davy's　discoveries。　　It　did　not　fail　in　producing　the　effect　foreseen　by　Sir　H。　Davy；the　preventing　the　corrosion　of　the　copper；　but　it　failed　as　a　cure　of　the　evil；　by　producing　one　of　an　OPPOSITE　character；　either　by　preserving　too　perfectly　from　decay　the　surface　of　the　copper；　or　by　rendering　it　negative；　it　allowed　marine　animals　and　vegetables　to　accumulate　on　its　surface；　and　thus　impede　the　progress　of　the　vessel。＇
  Other　instances　might；　if　necessary；　be　adduced；　to　show　that　long　intervals　frequently　elapse　between　the　discovery　of　new　principles　in　science　and　their　practical　application：　　nor　ought　this　at　all　to　surprise　us。　　Those　intellectual　qualifications；　which　give　birth　to　new　principles　or　to　new　methods；　are　of　quite　a　different　order　from　those　which　are　necessary　for　their　practical　application。
  At　the　time　of　the　discovery　of　the　beautiful　theorem　of　Huygens；　it　required　in　its　author　not　merely　a　complete　knowledge　of　the　mathematical　science　of　his　age；　but　a　genius　to　enlarge　its　boundaries　by　new　creations　of　his　own。　　Such　talents　are　not　always　united　with　a　quick　perception　of　the　details；　and　of　the　practica