became　glazed　with　ice；　yet　this　had　no　effect　in　checking　the　upward　whirling　of　the　balloon。　　Sunshine　was　beyond　the　upper　limits　of　the　cloud；　but　this　was　no　sooner　reached　than　the　balloon；　escaping　from　the　uprush；　plunged　down　several　hundred　feet；　only　to　be　whirled　up　again；　and　this　reciprocal　motion　was　repeated　eight　or　ten　times　during　an　interval　of　twenty　minutes；　in　all　of　which　time　no　expenditure　of　gas　or　discharge　of　ballast　enabled　the　aeronaut　to　regain　any　control　over　his　vessel。
  Statements　concerning　a　thunderstorm　witnessed　at　short　range　by　Wise　will　compare　with　other　accounts。　　The　thunder　〃rattled〃　without　any　reverberations；　and　when　the　storm　was　passing；　and　some　dense　clouds　moving　in　the　upper　currents；　the　〃surface　of　the　lower　stratum　swelled　up　suddenly　like　a　boiling　cauldron；　which　was　immediately　followed　by　the　most　brilliant　ebullition　of　sparkling　coruscations。〃　　Green；　in　his　stormy　ascent　from　Newbury；　England；　witnessed　a　thunderstorm　below　him；　as　will　be　remembered；　while　an　upper　cloud　stratum　lay　at　his　own　level。　　It　was　then　that　Green　observed　that　〃at　every　discharge　of　thunder　all　the　detached　pillars　of　clouds　within　the　distance　of　a　mile　around　became　attracted。〃
  The　author　will　have　occasion；　in　due　place；　to　give　personal　experiences　of　an　encounter　with　a　thunderstorm　which　will　compare　with　the　foregoing　description。
  CHAPTER　IX。　EARLY　METHODS　AND　IDEAS。
  Before　proceeding　to　introduce　the　chief　actors　and　their　achievements　in　the　period　next　before　us；　it　will　be　instructive　to　glance　at　some　of　the　principal　ideas　and　methods　in　favour　with　aeronauts　up　to　the　date　now　reached。　　It　will　be　seen　that　Wise　in　America；　contrary　to　the　practice　of　Green　in　our　own　country；　had　a　strong　attachment　to　the　antique　mode　of　inflation　with　hydrogen　prepared　by　the　vitriolic　process；　and　his　balloons　were　specially　made　and　varnished　for　the　use　of　this　gas。　　The　advantage　which　he　thus　bought　at　the　expense　of　much　trouble　and　the　providing　of　cumbersome　equipment　was　obvious　enough；　and　may　be　well　expressed　by　a　formula　which　holds　good　to…day；　namely；　that　whereas　1；000　cubic　feet　of　hydrogen　is　capable　of　lifting　7　lbs。；　the　same　quantity　of　coal　gas　of　ordinary　quality　will　raise　but　35　lbs。　　The　lighter　gas　came　into　all　Wise's　calculations　for　bolder　schemes。　　Thus；　when　he　discusses　the　possibility　of　using　a　metal　balloon；　his　figures　work　out　as　follows：　　If　a　balloon　of　200　feet　diameter　were　constructed　out　of　copper；　weighing　one　pound　to　the　square　foot；　if；　moreover；　some　six　tons　were　allowed　for　the　weight　of　car　and　fastenings；　an　available　lifting　power　would　remain　capable　of　raising　45　tons　to　an　altitude　of　two　miles。　　This　calculation　may　appear　somewhat　startling；　yet　it　is　not　only　substantially　correct；　but　Wise　entertained　no　doubt　as　to　the　practicability　of　such　a　machine。　　For　its　inflation　he　suggests　inserting　a　muslin　balloon　filled　with　air　within　the　copper　globe；　and　then　passing　hydrogen　gas　between　the　muslin　and　copper　surfaces；　which　would　exclude　the　inner　balloon　as　the　copper　one　filled　up。
  His　method　of　preparing　hydrogen　was　practically　that　still　adopted　in　the　field；　and　seems　in　his　hands　to　have　been　seldom　attended　with　difficulty。　　With　eight　common　130…gallon　rum　puncheons　he　could　reckon　on　evolving　5；000　cubic　feet　of　gas　in　an　hour；　using　his　elements　in　the　following　proportions：　　water；　560　lbs。；　sulphuric　acid　（sp。　g。　1。85）；　144　lbs。；　iron　turnings；　125　lbs。　　The　gas；　as　given　off；　was　cooled　and　purified　by　being　passed　through　a　head　of　water　kept　cool　and　containing　lime　in　solution。　　Contrasted　with　this；　we　find　it　estimated；　according　to　the　practice　of　this　time；　that　a　ton　of　good　bituminous　coal　should　yield　10；000　cubic　feet　of　carburetted　hydrogen　fit　for　lighting　purposes；　and　a　further　quantity　which；　though　useless　as　an　illuminant；　is　still　of　excellent　quality　for　the　aeronaut。
  It　would　even　seem　from　a　statement　of　Mr。　Monck　Mason　that　the　value　of　coke　in　his　day　largely　compensated　for　the　cost　of　producing　coal　gas；　so　that　in　a　large　number　of　Green's　ascents　no　charge　whatever　was　made　for　gas　by　the　companies　that　supplied　him。
  Some；　at　least；　of　the　methods　formerly　recommended　for　the　management　of　free　balloons　must　in　these　days　be　modified。　　Green；　as　we　have　seen；　was　in　favour　of　a　trail　rope　of　inordinate　length；　which　he　recommended　both　as　an　aid　to　steering　and　for　a　saving　of　ballast。　　In　special　circumstances；　and　more　particularly　over　the　sea；　this　may　be　reckoned　a　serviceable　adjunct；　but　over　land　its　use；　in　this　country　at　least；　would　be　open　to　serious　objection。　　The　writer　has　seen　the　consternation；　not　to　say　havoc；　that　a　trail　rope　may　occasion　when　crossing　a　town；　or　even　private　grounds；　and　the　actual　damage　done　to　a　garden　of　hops；　or　to　telegraph　or　telephone　wires；　may　be　very　serious　indeed。　　Moreover；　the　statement　made　by　some　early　practitioners　that　a　trail　rope　will　not　catch　so　as　to　hold　fast　in　a　wood　or　the　like；　is　not　to　be　relied　on；　for　an　instance　could　be　mentioned　coming　under　the　writer's　knowledge　where　such　a　rope　was　the　source　of　so　much　trouble　in　a　high　wind　that　it　had　to　be　cut　away。
  The　trouble　arose　in　this　way。　　The　rope　dragged　harmlessly　enough　along　the　open　ground。　　It　would；　likewise；　negotiate　exceedingly　well　a　single　tree　or　a　whole　plantation；　catching　and　releasing　itself　with　only　such　moderate　tugs　at　the　car　as　were　not　disturbing；　but；　presently；　its　end；　which　had　been　caught　and　again　released　by　one　tree；　swung　free　in　air　through　a　considerable　gap　to　another　tree；　where；　striking　a　horizontal　bough；　it　coiled　itself　several　times　around；　and　thus　held　the　balloon　fast；　which　now；　with　the　strength　of　the　wind；　was　borne　to　the　earth　again　and　again；　rebounding　high　in　air　after　each　impact；　until　freedom　was　gained　only　by　the　sacrifice　of　a　portion　of　the　rope。
  Wise　recommends　a　pendant　line　of　600　or　800　feet；　capable　of　bearing　a　strain　of　100　lbs。；　and　with　　characteristic　ingenuity　suggests　a　special　use　which　can　be　made　of　it；　namely；　that　of　having　light　ribbons　tied　on　at　every　hundred　feet；　by　means　of　which　the　drifts　of　lower　currents　may　be　detected。　　In　this　suggestion　there　is；　indeed；　a　great　deal　of　sound　sense；　for　there　is；　as　will　be　shown　hereafter；　very　much　value　to　be　attached　to　a　knowledge　of　those　air　rivers　that　are　flowing；　often　wholly　unsuspected；　at　various　heights。　　Small　parachutes；　crumpled　paper；　and　other　such…like　bodies　as　are　commonly　thrown　out　and　relied　on　to　declare　the　lower　drifts；　are　not　wholly　trustworthy；　for　this　reasonthat　air…streams　are　often　very　slender；　mere　filaments；　as　they　are　sometimes　called；　and　these；　though　setting　in　some　definite　direction；　and　capable　of　entrapping　and　wafting　away　some　small　body　which　may　come　within　their　influence；　may　not　affect　the　travel　of　so　big　an　object　as　a　balloon；　which　can　only　partake　of　some　more　general　air　movement。
  Wise；　by　his　expedient　of　tying　ribbons　at　different　points　to　his　trail　rope；　would　obtain　much　more　correct　and　constant　information　respecting　those　general　streams　through　which　the　pendant　rope　was　moving。　　A　similar　expedient　adopted　by　the　same　ingenious　aeronaut　is　worthy　of　imitation；　namely；　that　of　tying　ribbons　on　to　a　rod　projecting　laterally　from　the　car。　　These　form　a　handy　and　constant　telltale　as　to　the　flight　of　the　balloon；　for　should　they　be　fluttering　upwards　the　sky　sailor　at　once　knows　that　his　craft　is　descending；　and　that　he　must　act　accordingly。
  The　material；　pure　silk；　which　was　universally　adopted　up　to　and　after　the　period　we　are　now　regarding；　is　not　on　every　account　to　be　reckoned　the　most　desirable。　　In　the　first　place；　its　cost　alone　is　prohibitive；　and　next；　although　lighter　than　any　kind　of　linen；　strength　for　strength；　it　requires　a　greater　weight　of　varnish；　which；　moreover；　it　does　not　take　so　kindly　as　does　fabric　made　of　vegetable　tissue。　　Further；　paradoxical　as　it　may　appear；its　great　strength　is　not　entirely　an　advantage。　　There　are　occasions　which　must　come　into　the　experience　of　every　zealous　aeronaut　when　his　balloon　has　descended　in　a　rough　wind；　and　in　awkward　country。　　This　may；　indeed；　happen　even　when　the　ascent　has　been　made　in　calm。　　Squalls　of　wind　may　spring　up　at　short　notice；　or　after　traversing　only　two　or　three　counties　a　strong　gale　may　be　found　on　the　earth；　though　such　was　absent　in　the　starting　ground。　　This　is　more　particularly　the　case　when　the　landing　chances　to　be　on　high　ground　in　the　neighbourhood　of　the　sea。　　In　these　circumstances；　the　careful　balloonist；　who　will　generally　be　forewarned　by　the　ruffle　on　any　water　he　may　pass；　or　by　the　drift　of　smoke；　the　tossing　of　trees；　or　by　their　very　rustling　or　〃singing〃　wafted　upwards　to　him；　will；　if　possible；　seek　for　his　landing　place　the　lee　of　a　wood　or　some　other　sheltered　spot。　　But；　even　with　all　his　care；　he　will　sometimes　find　himself；　on　reaching　earth；　being　dragged　violently　across　country　on　a　mad　course　which　the　anchor　cannot　check。　　Now；　the　country　through　which　he　is　making　an　unwilling　steeplechase　may　be　difficult；　or　even　dangerous。　　R