At　the　end　of　November；　when　over　thirty　escape　voyages　had　been　made；　two　fatal　disasters　occurred。　　A　sailor　of　the　name　of　Prince　ascended　alone　on　a　moonless　night；　and　at　dawn；　away　on　the　north　coast　of　Scotland；　some　fishermen　sighted　a　balloon　in　the　sky　dropping　to　the　westward　in　the　ocean。　　The　only　subsequent　trace　of　this　balloon　was　a　bag　of　despatches　picked　up　in　the　Channel。　Curiously　enough；　two　days　later　almost　the　same　story　was　repeated。　　Two　aeronauts；　this　time　in　charge　of　despatches　and　pigeons；　were　carried　out　to　sea　and　never　traced。
  Undeterred　by　these　disasters；　a　notable　escape　was　now　attempted。　　An　important　total　eclipse　of　the　sun　was　to　occur　in　a　track　crossing　southern　Spain　and　Algeria　on　December　22nd。　　An　enthusiastic　astronomer；　Janssen；　was　commissioned　by　the　Academy　of　Sciences　to　attend　and　make　observations　of　this　eclipse。　　But　M。　Janssen　was　in　Paris；　as　were　also　his　instruments；　and　the　eclipse　track　lay　nearly　a　thousand　miles　away。　　The　one　and　only　possible　mode　of　fulfilling　his　commission　was　to　try　the　off…chance　afforded　by　balloon；　and　this　chance　he　resorted　to　only　twenty　days　before　the　eclipse　was　due。
  Taking　with　him　the　essential　parts　of　a　reflecting　telescope；　and　an　active　young　sailor　as　assistant；　he　left　Paris　at　6　a。m。　and　rose　at　once　to　3；600　feet；　dipping　again　somewhat　at　sunrise　（owing；　as　he　supposed；　to　loss　of　heat　through　radiation）；　but　subsequently　ascending　again　rapidly　under　the　increased　altitude　of　the　sun　till　his　balloon　attained　its　highest　level　of　7；200　feet。　　From　this　elevation；　shortly　after　11　a。m。；　he　sighted　the　sea；　when　he　commenced　a　descent　which　brought　him　to　earth　at　the　mouth　of　the　Loire。　　It　had　been　fast　travellingsome　300　miles　in　little　more　than　three　hoursand　the　ground　wind　was　strong。　　Nevertheless；　neither　passengers　nor　instruments　were　injured；　and　M。　Janssen　was　fully　established　by　the　day　of　eclipse　on　his　observing　ground　at　Oran；　on　the　Algerian　coast。　　It　is　distressing　to　add　that　the　phenomenon　was　hidden　by　cloud。　　In　the　month　that　followed　this　splendid　venture　no　fewer　than　fifteen　balloons　escaped　from　Paris；　of　which　four　fell　into　the　hands　of　the　enemy；　although　for　greater　security　all　ascents　were　now　being　made　by　night。
  On　January　13th；　1871；　a　new　device　for　the　return　post　was　tried；　and；　in　addition　to　pigeons；　sheep　dogs　were　taken　up；　with　the　idea　of　their　being　returned　to　the　city　with　messages　concealed　within　their　collars。　　There　is　apparently　no　record　of　any　message　having　been　returned　to　the　town　by　this　ingenious　method。　　On　January　24th　a　balloon；　piloted　by　a　sailor；　and　containing　a　large　freight　of　letters；　fell　within　the　Prussian　lines；　but　the　patriotism　of　the　country　was　strong　enough　to　secure　the　despatches　being　saved　and　entrusted　to　the　safe　conveyance　of　the　Post　Office。　　Then　followed　the　total　loss　of　a　balloon　at　sea；　but　this　was　destined　to　be　the　last；　save　one；　that　was　to　attempt　the　dangerous　mission。　　The　next　day；　January　28th；　the　last　official　balloon　left　the　town；　manned　by　a　single　sailor；　carrying　but　a　small　weight　of　despatches；　but　ordering　the　ships　to　proceed　to　Dieppe　for　the　revictualling　of　Paris。
  Five　additional　balloons　at　that　time　in　readiness　were　never　required　for　the　risky　service　for　which　they　were　designed。
  There　can　be　little　doubt　that　had　the　siege　continued　a　more　elaborate　use　of　balloons　would　have　been　developed。　Schemes　were　being　mooted　to　attempt　the　vastly　more　difficult　task　of　conveying　balloons　into　Paris　from　outside。　　When　hostilities　terminated　there　were　actually　six　balloons　in　readiness　for　this　venture　at　Lisle；　and　waiting　only　for　a　northerly　wind。　　M。　de　Fonvielle；　possessed　of　both　courage　and　experience；　was　prepared　to　put　in　practice　a　method　of　guiding　by　a　small　propelling　force　a　balloon　that　was　being　carried　by　sufficiently　favouring　winds　within　a　few　degrees　of　its　desired　goaland　in　the　case　of　Paris　the　goal　was　an　area　of　some　twenty　miles　in　diameter。　　Within　the　invested　area　several　attempts　were　actually　made　to　control　balloons　by　methods　of　steering。　　The　names　of　Vert　and　Dupuy　de　Lome　must　here　be　specially　mentioned。　　The　former　had　elaborated　an　invention　which　received　much　assistance；　and　was　subsequently　exhibited　at　the　Crystal　Palace。　　The　latter　received　a　grant　of　L1；600　to　perfect　a　complex　machine；　having　within　its　gas　envelope　an　air　chamber；　suggested　by　the　swimming　bladder　of　a　fish；　having　also　a　sail　helm　and　a　propelling　screw；　to　be　operated　by　manual　labour。
  The　relation　of　this　invention　to　others　of　similar　purpose　will　be　further　discussed　later　on。　　But　an　actual　trial　of　a　dirigible　craft；　the　design　of　Admiral　Labrousse；　was　made　from　the　Orleans　railway　station　on　January　9th。　This　machine　consisted　of　a　balloon　of　about　the　standard　capacity　of　the　siege　balloons；　namely　some　70；000　cubic　feet；　fitted　with　two　screws　of　about　12　feet　diameter；　but　capable　of　being　readily　worked　at　moderate　speed。　　It　was　not　a　success。　　M。　Richard；　with　three　sailors；　made　a　tentative　ascent；　and　used　their　best　endeavours　to　control　their　vessel；　but　practically　without　avail；　and　the　machine　presently　coming　to　earth　clumsily；　a　portion　of　the　gear　caught　in　the　ground　and　the　travellers　were　thrown　over　and　roughly　dragged　for　a　long　distance。
  Fairly　looked　at；　the　aerial　post　of　the　siege　of　Paris　must　be　regarded　as　an　ambitious　and；　on　the　whole；　successful　enterprise。　　Some　two　million　and　a　half　of　letters；　amounting　in　weight　to　some　ten　tons；　were　conveyed　through　the　four　months；　in　addition　to　which　at　least　an　equal　weight　of　other　freight　was　taken　up；　exclusive　of　actual　passengers；　of　whom　no　fewer　than　two　hundred　were　transported　from　the　beleaguered　city。　　Of　these　only　one　returned；　seven　or　eight　were　drowned；　twice　this　number　were　taken　prisoners；　and　as　many　again　more　or　less　injured　in　descents。　　From　a　purely　financial　point　of　view　the　undertaking　was　no　failure；　as　the　cost；　great　as　it　necessarily　became；　was；　it　is　said；　fairly　covered　by　the　postage；　which　it　was　possible　and　by　no　means　unreasonable　to　levy。　　The　　recognised　tariff　seems　to　have　been　20　centimes　for　4　grammes；　or　at　the　rate　of　not　greatly　more　than　a　shilling　per　English　ounce。　　Surely　hardly　on　a　par　with　famein　prices　in　a　time　of　siege。
  It　has　already　been　stated　that　the　defenders　of　Paris　did　not　derive　substantial　assistance　from　the　services　of　such　a　reconnoitring　balloon　as　is　generally　used　in　warfare　at　every　available　opportunity。　　It　is　possible　that　the　peculiar　circumstances　of　the　investment　of　the　town　rendered　such　reconnaissance　of　comparatively　small　value。　　But；　at　any　rate；　it　seems　clear　that　due　opportunity　was　not　given　to　this　strategic　method。　　M。　Giffard；　who　at　the　commencement　of　the　siege　was　in　Paris；　and　whose　experience　with　a　captive　balloon　was　second　to　none；　made　early　overtures　to　the　Government；　offering　to　build　for　L40；000　a　suitable　balloon；　capable　of　raising　forty　persons　to　a　heightm　of　3；000　feet。　　Forty　aerial　scouts；　it　may　be　said；　are　hardly　needed　for　purposes　of　outlook　at　one　time；　but　it　appears　that　this　was　not　the　consideration　which　stood　in　the　way　of　M。　Giffard's　offer　being　accepted。　　According　to　M。　de　Fonvielle；　the　Government　refused　the　experienced　aeronaut's　proposal　on　the　ground　that　he　required　a　place　in　the　Champs　Elysees；　〃which　it　would　be　necessary　to　clear　of　a　few　shrubs〃！
  CHAPTER　XIX。　THE　TRAGEDY　OF　THE　ZENITH。〃THE　NAVIGABLE　BALLOON
  The　mechanical　air　ship　had；　by　this　time；　as　may　be　inferred；　begun　seriously　to　occupy　the　attention　of　both　theoretical　and　practical　aeronauts。　　One　of　the　earliest　machines　deserving　of　special　mention　was　designed　by　M。　Giffard；　and　consisted　of　an　elongated　balloon；　104　feet　in　length　and　39　feet　in　greatest　diameter；　furnished　with　a　triangular　rudder；　and　a　steam　engine　operating　a　screw。　　The　fire　of　the　engine；　which　burned　coke；　was　skilfully　protected；　and　the　fuel　and　water　required　were　taken　into　calculation　as　so　much　ballast　to　be　gradually　expended。　　In　this　vessel；　inflated　only　with　coal　gas；　and　somewhat　unmanageable　and　difficult　to　balance；　the　enthusiastic　inventor　ascended　alone　from　the　Hippodrome　and　executed　sundry　desired　movements；　not　unsuccessfully。　　But　the　trial　was　not　of　long　duration；　and　the　descent　proved　both　rapid　and　perilous。　　Had　the　trial　been　made　in　such　a　perfect　calm　as　that　which　prevailed　when　certain　subsequent　inventions　were　tested；　it　was　considered　that　M。　Giffard's　vessel　would　have　been　as　navigable　as　a　boat　in　the　water。　　This　unrivalled　mechanician；　after　having　made　great　advances　in　the　direction　of　high　speed　engines　of　sufficient　lightness；　proceeded　to　design　a　vastly　improved　dirigible　balloon；　when　his　endeavours　were　frustrated　by　blindness。
  As　has　been　already　stated；　M。　Dupuy　de　Lome；　at　the　end　of　the　siege　of　Paris；　was　engaged　in　building　a　navigable　balloon；　which；　owing　to　the　unsettled　state　of　affairs　in　France；　did　not　receive　its　trial　till　two　years　later。　　This　balloon；　which　was　inflated　with　pure　hydrogen；　was　of　greater　capacity　than　that　of　M。　Gif