575 Vol. LXVIII, No. l ~ . ] AND RAILROAD JOURNAL,

AERONAUTICS. U1Wlm thi s ltelld iug we sh all he rea fter p u hlisli a ll matter

rela t ing to t he in ter esting su bject o f Acri 11 ~a l'ig ll ti on, a

b runch of en gineeri ng which is ra pid ly in creas in g in go ner: I

in terest. )i r. O. lum ut " C . I·~ . , of Ch icag o , h us con se nt ed to

net as Associa te E d itor fu r th is depa rtment, and will be a Ir e­

qu ent con t r ibu tor to it ,

R eader'S nf I1d,~ depa r tm en t 1I!"t} ;·U1UCR!t·d to senti tl.c na mes and add resses of per.'v II S in terested in I1/fJ subject (1Aeronau t ics to tlu: }l1/vli sh, r vj 'I'm: .\ )IEIlIl: .\ X E X GI X E LH.

WHY IS ART IF iC IAL F L IGHT SO DIFFICULT OF INVENTION?

B. OTTO L U,I E.-T ILU ,. *

11' is indeed rl illlcult for man a tlil th ro u g h th e r ealm o f a ir w ith th e freed om o f a hi rr] ; bu t th o I O ll,~in g to (10 so will allow u s 1I0 rest , A s ing le la rg e b ird ci rcli ng over ou r h ea d w ill ren ew in us th e wi sh t o sa a r li ke it ill th e firm a men t .

The mecha nical ins tinc t II I even th e ave ra g e m an is su tll­cie n t to pe rcei ve tha t We 1et ,1 ba t to lin d the r ig ht key to u n ­lock fo r ou r use a n cu t ir cl . new pl ll·ta ! of w or ld -wid e com m u ­n ica tion . Do we not se e w it h w ha t ca lm , w ith w ha t com ple te ussura ucc a nd wonder full y s imple uinnreu vres y onder bi rd is

t ry to ut il ize ou r dea r ly bo u g-ht w isd om in a c tual tli ght, our luck of sk ill is p a in fu lly d is pl ayc«] ; the s wa llo ws lly a ro und our hc.uls and twi tt e r th e ir d e ris ion . There is prob a b ly no oth e r h ra nc h of eng inee ri ug in w hi c h it is so dillicu lt to lind th o righ t a p p lica t io n o f our th eo r ies in uc t uu l p ra c tice .

'l' 0-7Iay we k now very wel l w ha t sup po r t: th e 11 ' ing b ird ; h is wi ng c leaves t ho a ir at g rea t s peed , a n t! hy the sle nd er c u rve o f it s profil e compels th e uccc ssury s us tai n ing reaction, oven in th is th in niediurn. Th e w in d w hich pa ss es unrl er the w id esp read sa il-su r faces o f th o l.inl und erg oes a g en tle d evi a­ti on o n the conc a ve low er sur face o f t he w ill g , wh ich resu lt s in n. su lllc icnt " li f t" w h en t h e wind is s t r ong enough. T h e bea ting o f th e wi ng complcnu-nt s w ha t th e nail uction a lone docs not nccoiupl lsh.

T o the untrained o bser ve r , it is tr u e, wl icu he sees the bird in tli g'h t" th e m ov em ents o f th e w ings see m to be s im ple u p­unrl-down mo t ions ; bu t th e av ia tor co m bines the wi ng heats w ith the efl'cc t of the vel ocity of !l ig h t unrl th e m ovem ent of t he a ir , nud concl u des th at e ven in row ing flight, especially fo r tile la rg er b irds, til e carryi n g su rf aces cut the a ir a t a ve ry acu te an g le, nnd th ut in ra pi d for wa rd Iligh t e ven a gen t le-d e­p ression uf the wiu gs prod u ces muc h ca rry ing power w ith littl e expend itu re of ene rgy .

'I' his, the refo re , is the ac t ion to im it at e . this rupld for wa rd m otiou, wi th slow be a t ing o f the w ing-at k-us t, t h is is w h a t nntu ro tea ches us ; but it is on ly in case tha t tho process is ca r ­ried on wi th a bso lu te co rrec t ness th a t w e lIlay h op e to tly in this w ay . If uny th ing be om itt ed or in cor rec tly clone , th e whole u uelc rt ak in,1" will f ail.

W het he r th is d irec t imitut lo n of na t ural rlig ht is one W l\Y

ou t o i uiunv whicu will kn't us to th e g oa l, or w he th e r it is the on ly W;\y , is toclny s t ill a mooted q uest iou , lIla ny a vi ­at or s, f or instance. co nside r the w iug mot.i on o f b ird s too d itll­eu lt"to! irnit a te mechanically , am! t hey d is li k e gil' ing up for

- ae r ia l prop u lsi on the ~~ .~~------_.-------~----~---------- --- _ .. - -.- - ------ -- - - - ------- .-

F ig . I.

sc rew pr o po l ! e r • w hich has bee n Io u n d so usef ul in th e wn­tor, On one p oin t, h oweve r , they are ugrccd , and th a t Is th a t we mus t lIy at hi u h speed if we fire to tly a t a ll, and this ruq uircmo ut i II clan ­ue r fu l d llllcul y in th o in ve ntion o f u r t i­Ilciul tl ig h t .

It i.~ u ni ve rs ally ad ­m itkt! to -day that m.m will u ot he uble t tl ri so ver t lc nlly in culm ai r from II p os i­ti on u f rcs t ; 110 more .-nn t he larg o birds d o so , . beca u se th o e x ­peudi t u ro o f energy IIl U S t he enormous . ])( 's ig n fJ!":1 o f Hy ing inachinus, for t h is Jcason, uow arrange the-ir a p para t us so as 10 hcu iu to ri se witlt :L eoi;s itlc ra ble h ori ­zo n ta lmot io n .

. I t ho u g h mos t l'I"uj"ds of t lu: k irul .ue l ,a, c(1 u p on t he I'ri n .ip lc o f h i r d­lli /.!:h t- i .e" th e sUll­po r t ing p owe r is o h­

g lid ing : tllI ung h tIll: ai r 1 t ':In it 1,,1 t liu t m.ui wi \! never be able to aeeo lllp lis lt :IS nlll l'! l 'I - llla n , will I :tl l h is hl' as li' <! inlc'Ili­i;CIll't1 ~ ll ll i w it h a \! the llll:l.,han i,,:d :tid:; tlt a t, ha \'l~ cn:ll,l",! him to LJ n ill[ trlll y Ill:l r \,"[[ 1)115 II"(} I' I;" I ;\ nd s t ill it. j<.; diIJi<:l1lt-­[ may :' ay e xc,', :d in g ly d illk lilt - to 1"I '[ 'ea t ( '1'['11 apl'ro:dlll:ltcly w ha t ll:ltll W PCl'fOrJllS :,, ) <::I:; il)' . 11 0 11' n t:lny v:tin "tfort" I"!\'tl 1,,;ell mad e tn i lll it:ll <: t lte hin l I Th is , t (l O, 11011' th :lt ,eic-ncll h as se ri olls ly ta ken lip t id :; l{1 l1's l iOll ; t.ha l. th e phe: llOllH'Il:1 of nat ll r:d 11i!d ll. hay" l,,'c ll .I i, '('I ' cd , 'Ina llllll i(':l1l1' :tlltl lllc cha ll i­(~ [!l y . o!,t ic a ll y a llil hy ins :lIl a l)"On" p h fl t fl~ra-!,hs , ;1.0 we ll a" ;;ra ph iea !ly hy ..lec t r i<: rc(:ortl,' . l ' I) \\" a t las t, " 'e lia n : pr o ­,~ ressC' d :;o fal" t hat t ,e: [>i i'll ("lllll" t, n ti:lt:: lli lis as to t ite theory , but ill [lr:lI: t iee " h e h:1.' l lil) lallg h un l!>;. " A'i soon a:; II -e

t.ii ncd by sa il -sur ­[ l tl :" , rupi.l ly mov. «] for w:ml - still the nu-Lli o.Is o t repro­d lll: illg" n.u u rul il i!" lt t hy nll ' elt: lIIi.::d me.ius are as ur io u s a ·~ th e a l'i :tt.rll,s WilD Illld i' rt a ke tlw l ! "l' ('r inlent~, eac h lIlan bo i n!~' lt i ~ OW l! wa y ; IJ\lt an t ltc ,, : ~ ( ' parak w ays y e t le:lll to 1I11t) a nd Ih l: Sil 11 ll: !'I'c f, IIIl w h i" lt ti ll) ' :0 1l ('I:pt ion and of te:n th e in gen io us \'e>",,1 itsel f is wreek"d lJdnr r> i i, "a n iJt) uti li zed for tl lu in l< '11l It,<I 1'111"I >oses , Tnd ,)" t! they rarf'i ,\'. ,d tho u t iJreak ing tlw 1I\ ' lC' lti lll:, ge t h())"on ll tlt o li r~ t tr ia l, " ' h k h lIsu all y results in ti ll: fa illlre tu rb l: i llto th t: a ir a t all, ur a t I J( ,~ t to g et bil (: k

to the ea r It n ' ry 'lllil :k ly . . \\' ha L it me" I!:; to ; J:; w h in .ing through ih ,: a i l' w i t I th e ve­

loci ty of an / ' X pre .';S t rai n , a IH I the n to Cllnll: ),,,:k to the g ro u nd w it h o llt <l an g eI' :'Ill<l w itho u t lt re a ki:Jg the a p l'Hra tus . ie is not ,Iiflicu lt to I;onc(:in!, .It tl Ji,,~ tr ic k is to he d one ,l i th a l:Jq ; e , h elLvy, a!leI eomplk :\[ell lIlach ille, the l' l"l!sped o f :llig h ting

576 Ot,...aWes. 4na A rch IY ,Jes MU~ I: UIt\

THE AM E R I CAN ENGINEER'· [ Decembe r, xeq4.

. a fuly is, of course, nn u-h less. It sec,Ill' rea lly prr-pus rc r uus to count Ull SII(;,' '',' S i ll t he li rs t lr i,d" with sUl'h co rnpl icutcd machi n.-r v ; for th is l'l'a S(11l th e reviewer in ~ " 0 , :!:,:) o f Pro mc­the IS is ,jll i: e r i,ght in h is -t .ucu ie u t t h a i , by ('XIH'l'illll,n t in g

F ig . 2 .

: Fig. 3.

w i tl ll l a r .~ " Ill:ll'h inl'. , t l:o 1'\J "' ns n f Ihe tuitiu n , whir-l. I \' I~ lIl11s t surely flay il,.fo l" · II'I ~ "a m l u ivv I I", i s usc h-s- ly in ­l)

e re'a sc'd , ~[ a,i ll l'" ll .\ i n .c: nuuhim-, t hn I,n ', '" llll lled to ill III" uh n vc -tue n t iotu-r! rcv iu w, h :IS ( ' { ISt.~ ""(O ry Jargl ' <u ur n f 1I1U J1(' . ,

an d I. hiH di Ht illt-;lIis h" d ill l" 'lI l ,,!, d l','I' n ' (Os hi g h !,I':ris(, for hu v­i ll g d .:w ,li 'd .: C) muc h h , n v int i .n, I I e h ith erto Ciud cre llu o(

cng inc"r ing sc icncc : but, after all. th e resul t o f h is lab or s ha s oul v hccn to show us .. how nut to do it ."

' (' h is cclc hrnted «xnmplo may su tllce to de monstrate that th e ' lIlost ingeniou s m.rch inc ry , eve n whe n co m hined with po we r­

• f nl and \'cry light III 0 t o r s , will no t alone so lve this in ­t rie a te p r o b l e m , :\1a x i Ill ' 8 ex pe r i­mcnts a lso p ro vo the tru th of a nothe r view , w hic h I ha ve a lluded to a t every o p portu ni y : tl ,at , in po in t of fa ct, th e rea l dest royer of t h is m ac hin e , weigh ing 8,000 lbs. , w us a gen tle wind g us t , w hi ch , in con ­seq ue nc e 0 f th e enor mous ly I a r g e w ind su rfaces, p ro ­d uced a ve ry g rea t f o r c e • T he run­ch ine cou ld not fail co ming to g rief , ami it will Iuvurfuhly COIllC to g rief w hen ­ever it bused ev en in a modcra te wind ,

l "O W , which one of all t he in venters of suc h a p pa ra tus has the p roper con­ce ptio n of the mer ­e i lcss ness 0 t t· h I' w ind to wnrr l nll tl r ;

ing- machines ? T h is laings u p a new ditllcu lty in t hu in ­vcntion ot ar t ificia l flight . I Ill y s e lf hnv e o ften enough been th e plaything of t he wi nd , when r w as ta ke n un ­a wares d u ring Illy e x p e ri m e n t s by wi nd rusts : sud ­rle n ly was ' ra ised t he heigh t o f a h ouse a n d tossed ha ck uiu l fur t.h, so th a t I wa s h renthless n n t.il I got.u S( '11 to the SCIl­

sa t.ion . I u such ex ­pcrhucn ts O Il I} cnn ­nut fail to become a ll a ir-gy m nast ill the bolde-s t sense of the wor d, find I ma y th ere fo re bo pe r ­mitred to ex pre ss my op inions OIl the uction o f the wind lin aerop la nes, , 1111 011 the best w ay o f cOll lllemctill" it" d"sl r ue t lve Iort:n,

I [err A lisd t iilz , 011 S"ptc lIlhl"r Hlh o f , 1 1i ~ 'ea r ( IS!!I), a vailed h im self o f nn oppnrt unity o ( :tldll , ' ,. OIllC photo­g ra l'h ~ of my exer­II i :; I' s i n wi n d j"

we.uh r . The i l­I11st ru tions , tig:4 . ;;

, , . , urul Ii, n ,prod llC'ed i rruu h i" mstnntnncous \ ' 1"11 ' " <how wh :iI; .r vruuns t i« fr':lt " a m JII.'I '('Ssar)' to ke llfl f rol ll I Il · ill .: ~ 1.1 11' 11 1111 rro lll ' t1I1~ ~ad dJe ill ~ lI l lh a ~ '1 l1 a ! ly ri lk '.hrOll}.dl t il" ai r , a nd to I'r ing hack, Iurt hc rruoru, III " lI y JIl! ( on tIl! sak ly to 11 111 11 11 '1' eart h, 'I' Ju-so fad ors e.u ui u t, fl", sih ly lx: !1l',o;J el:kd by uny one wh» t ries to rlirr 'cl a ll ncrinl veh ic le th ro ugh movi ll g a il',

- - - - -- - - - - - - - ------------

577 Yol. LXV lIJ. No. 12.] AND RAI LROAD JOURNAL.

I f wc co u l.I no t c o n vi n.:« Ol l r ~ eh (' s .l.rilv how easily an'! s a fel y hir. ls dart a bou t in t he a ir :HIII <:omnianel (-Ill: wind, we ~igh t re.il ly d e" pa ir of the in ven ti on o f ur titkiul /li ght. But IS t here any n 'al p rospec t that w e w ill a tt ai n to their ski ll '? ' ' 'ha t a rc th e real u l t im nt c a ims o r uv i.u ion '! T o what d e~ ree or pe r fe ct io n w ill i t. ever he p oss ible to d e vel op human !!ig "h l ? Yes to dcu [uji , for th at is the o rr ' .t ex pres s iu n , and .le ­ve lo p m c n t i s t h ,: c o rr e c t li n e of thou g-ht, hy follo w -In g w h ic h w e m a y ach ieve s uccess in a viati o n .

N o on e can fo re ­see to- d a y how far m a n wi lt" he ahlo to ed uca te him sel] in flyi n g . hec.m se h i th­e rt o m uch to o l it t le w o rk lias bee n do n e in ac t u .il p ra ct ice , Even tho ng h , here' and th e r o , sorn« sche me m a y h nv o bee n act ua l ly cu r ­r ied ou t , :Ln ,l Ih cn w r e c k c d o n t he li b a ye - me ntion ed roc k, let t h is m ea ns v ery liu lc for t h c d e ve lo p m e n t o r dy ­namic lIig h t. As to the r es t , th ere is a g-oo,l Ile al o f t heo ­ri zi n g , whic h nl so docs yc ry li t tl c g oocl in t he p re se n t s t a te o f t he a r t.

A s fa r a s the the­ory o r fl igh t 1.0 co n ­cerncd , w e arc to ­Jny no t a t all h:u lIy o ly. Sin,,,: we have

und the p roperty o r it s c ur ved sect ion in eco nolll iz in g e nc ru y , we ca n ex p lui u 'Il li te c learly all the phenomou n o f n ut.uru! JIig h t. \ VIt:\ t we must now he~ i n to develop ,, 1) init io is a ctual p rac tice in lli /-(ht. 'I'h,' ,lil1ir:ul Lies that co n fro n t u s no w a J'( ~ o f II p u rely p ruc ticn l u.uure , hut they a rc: g n 'a tcr than they Sel'nl to be a t firs t b lush. \V I) m ust mn k o a speci a l s tu d y of these p rac t ica l , li tlieult ies , w e mus t d ev ise m e th od s o f in ves t ig a t in g

t• t he m t horou g-h ly in or.ler to coun teract t hc lll: .s u cc C8s fn lly .

],C to a limitr-I extent, In Ibis way we will gal]lI-r l'xl'cril:n('c as to stn l rili ty in fligltt, as to the action of t ile wind, .uid as to sa fe ali g h t in !; : a nd thus , by (,lJll.st:<Ilt, iruprov.uunt., gr:lIlnally c om e closer to con t ln ucd tli g lu.

T h is eons u nuu utio u ca n not IJe violently lJro u~ Jd nhout. It is j u s t because t ho in ventors of l1ying machines usuu lly expect

bee n e nl ig h tened us to the a ir resi s ta nc e' und er th e b ir. l '8 win ~

F ig . 4.

too g reat illlllledi :lt" result s fr om the ir "P I"l ra [ tlS t hn t th e uctuul ac h ic vcn u-nt s aI' '' so smnll . The n :lIl" inin g' in th e air without a b .rll oon , a n,l e r u is illg ul iou t th ro ugh th e .n m os ph cr« . is a f1 eld o f w or k 50 nove'! t lmt w e w ill lin d OU I' lle ari n ,~s th erein onlv l i v dc !.{rcC' s. \ \~ll I.H·\'C~r l1 (' g l l' c t ~ the idr -n o f :L

It;_~(lithy rle\:clolllllci i t of the S('.i(~llCC IJy ' c o ll :~ L lI j t.l y l : :Cl'(';L s:ng ou r cx pcr icn ce on th» ,.Ial,ilily :<l1I1 ,'"fety of movement in the nir , will neve-r .ucom plish :lIlytlling in this licld.

T h e methods which I Im vo l'mp(l_~cd .uid pl'act ised. in or d er

_ J Fig. 5.

()n]y l:in ' Ud" W:Ly wi ll w e i", a hle to oo \\, t lu: 1'i:;l>t "c-ed ill l it i, n o ,...... lUl{ \rndl tc i ng tu-l.l . ~ No lIl:Lf.tl ' r ho w p r ill, it il 'l'!y it Illay h, 'g ill, t ill' lIlI,thu'] which runy l. -.ul UY " r " :ll tlig h t m uxt I " , ,,,'p ,,l d,, uf ,]"n;]uI,lllClIt. Fo r thi ~; fl':l,'iOll t lln 1'. pt~r i Il u :ll t:~ whieh we l1ia k n H l tls t gi ...·c us ::n 0pllllrtlil lity of :L, :Lu:d ly Hyi ng- tlll'llllg-ll t.he a ir , cven if it

Fig. 6,

tlrut, i le~iIl ni ll g \'·;it l l -I m r t f! i~ J tf : ~ , I Ini.~ ltt ex tend l Jl,'r i O l lrr J(: Y ~ to g'l'i'a V'l" dis t:l ll(:( : ~ , an : k no w n ( 0 t. h« ['l'aders of L'ro.. ., (/I{ I/ S, '.;. I ron : m y u r t iolc s i ll N o. :;It.i a lld :\0 , '2'21) uf t.hisjnun:nl. I \\' il l , t lurc ­fo re, o nly u u-n t.iou iJri c lly a ll'l'f>"ll t Ill}' Iu rt lu-r cx pr-ri m .-n ts.

" A German p.'Llll'r in w llich IllC ori gi Jlal of th is iP'tk:c \'Ili. !i puhli ...\iCI1.. : [

I

578 T H E. AMERICAN:.,RNGINEER [ De cember; I 94.

. \ ft<- l' I ha d d .-till itd,' " ' IT r l" illed {II' IIlI' t r ia ls th al !!Iid ill" fliu h t is f('ao.;ilo l" fW1 1I I ~ic' , 'at<-t l P"i lll ' . ' ,,-ili ; I[llil" a ,ill;iJ1l: : q ~ pnru t us a nd ill IlInd " I:Ill: wi n r!« t lu-re I....-r« t wo Iu rt lur proh­I('IIIS 10 he a ll:lt :k "11. I n th e li r" t pl :w c, t his s a ili n ~ e x e-rc ise m ust hll ,'x lel lth 'd 10 ,' t ro ll,:;I'r w in.Ix, ,,) as , if no. ' ihlt' , to Tf:aeh t he ,·n.lllillll( ·11 so aring' wh ich we so greatly rulmir« in b in ls : awl . III tilt' SI'COIIII pla el' , we must endeavo r to com­pi m en t s lm p lo sa i!ill,:; lIigl l t hy dyn.uni« means , so a s ,~ r " d · ually 10 reur-h a " I nt im u-il IIi,:.drt , e ven when t h e a ir is cnl un -r .

: 1-'111' t h is p llrp llso: it w as IIN'I',;sary to ha ve a propl: r lIyill ;:;,nll poin t Ilea l' l lc r liu . 1 ha ve !lOW co nstru ct ed such a po iut, hy

-- -­ - '--_... _ '­ - - - - - - - -------,

F ig . 7,

b u ilt li ug; a u n rt ltlc inl 1' 0!lk:,1 hill , .• 0 ft . ill lll' i,,-,;h t, ill G rl's s­Li l'h rfr -ld «, tn the east o f th e .\lIhal t Ra ilway . The sha llll of th is hill, nm l t ho nuu u u-r ill w hi ch it is usr-rl, ure shown ill figs. 1 a lld ~ . l ' nd c-r t ho ttJp or t he h ill, w h ich is sod ,\ud 01'1' 1', t her e is :L t iiub 'r ed «lun uh er. aCet'ss ilJ!r: f rom t he rea r, in wh ich Ihll a p pa rat.u s is s tored.

.b s hown in Ii:' . 7, a rUII is tal"," to the "rl g e o f t he sodll illg in l'er fol'l ll illg I h" "x, 'rd ," · ·. F ig . S shows th" insta ut o f Llm l­in,!! , wheu th c sa il ,s u r fa ce s arc t ipp ell up to th e fro n t , in o rd e r to l'lI"ck t he w !o<:i ty o f tho lIig h t .

.\ 11 :I[' p" ra t us l'i th an Iltt aCh lJl('lIt :lI ra n;; ,-,1 fo r ro wing lIigh t has a lso 1"~" lJ :lI't ua lly t('st ed . F i;;s , :l lllJd .[ s ho w th is a ppa­ra tlls hlll-h 11'1 " '11 fold l:d a ud when }:pread u u t to i t.~ f u ll e .- 'n t .

/

'l' he.d is ta. II" · 10 I," " " II . lI' i U ~ 'lips is ~ li II. :: ill . 'I'h ,) I l a p p i ll .' ~ lllot lOl1 " t th r' Will"'S 1-; p ro<!III'I' e! 101' a IUOl< J1' e!ri" t'll Ill ' CO lli . p re, sed (':lrl "lIIi" ac id , ' :1' , 1';XI; j' l,t ( Ill' the adclitioll 'l lf Ih n I'lJ w illg d t' ' il'l' , Ilis :'1 I":tr:t! ' :.. i., 10 II ilt. '1l1 ile lik e m y fOl'lllc r ' ap pa r:, Lll s , .\ I'I'I's ," ll r" w il h :1 li l l ~ j ' r s la r . t1 11 ~ Ila l'pio g of ~h e '; lIlg ,' , a lld : 1. ' 10 Ih" l'I's l" th , ' halldli llg- o f h i:, 'LJ "l' a ra t lls l ~ Lh" ,': ~l\ " as ,Ih a l. 'Jf II,, ' s ill'l ,Jr' r flll'lil ' , . ' '' \'<: r lh" k-s" , Illy IIrs t "a llt ' " Il, l'I,d ', i'1'1t.," , 't! to 1111 : ( ila t. if [ ha ',! 1101'1 II" U Illys,'lf i llto Ih,- a ir w il h Ilai'l' ill'" \ · illg s . w ilh' Jlll (1Irth , 'r p l'l:('a lll io us, t he IU:lch ille " 'o ll ie! p l'lJI<: d tly ha n : I'l':wh"d Ihc bot to lll ill the conditiu l! 'Jf a '.. c" k. 'l' h l' rl: a re a lways new, u nc " pcc! ed

ig .8

Iea tu res , ami a single d isa s tro us luud ing w ill ruin the w h ol e much inc. Here, a ga in , we urc re minded that we mus t n ot make too ~ re :l t demand s upon the m a ch ine a t first. 1 had . theref ore , to conten t m y se lf a t firs t w it h u s in g th is la rgcr am i hea vie r machine, w hich welghs 88 lbs, o r t w ice as m u ch as m y s im p le sa iling outll t, for ini ti a l pla in g lid ing. T h us 1 tlr s t pract ise d a lig hting sufcly , and now, nftc r gcuiug th us far , 1 pe rmit m ys el f to begin bea ti ng the w in gs cautiously. in actua l tligh t.

T here llIay, o f course, be ot he r li ucs in w h ic h a r ti ficia l human Bigh t may be developed lo gically. S im ila r problems Will , h owe ver, huve to bc so lved in auy case before th is di tli ­cu l t ta sk is accomplished. T h u s, f or iustunce, m uch energy is bein g devoted to th c q u est ion o f rcgu lu t im; th c 1\igh t me­

, chanically, so th at thc equilibrium .uny uot be dep end ent up on the sk ill of th o op era tor. W e ca n on ly ho pe tha t th is impor­tant, ult hough extremely d ltll cu lt , under ta k ing may succeed , for th en th e p rob lem o f uvi ut iou w ou ld be much s im plified.

Wha te ver be th e pa t h ado pted , progress cun o nly lie e x ­p ec ted w hen the experime nts mndo adm it uf u sef ul obsc rvu ­t ion s c onc ernin g t ho phenom enu per tai n ing to a bod y tlyi ng fr ee throug h t he 111 1'. Ther e uro lllu ny e n t ir el y ne w co nd i­t ions to be con side red w h ich 10 n ut co n fro n t us in ot he r b run ch es of cug inc er iug , s uch as sa fe :1Il(1 s tab le t1ig ht agu in s t all th e irr egu larit ies o t t he Wind , a nd th e a lig h t ing w ith ou t ri sk w h en IlyIng dynn mi cully, T h ese a rc p o ints on whic h ve ry li t tl e uctuul e xpe rience is a t hand , .uul y et these w ill be found t il be the ve ry essenc e of p ract ica l a vi ut ion , 'I'h is fen ­tu re will assured ly make m orc d itli cult t11 0 so lution o f t hc prob lem or n rt iflci al lligh t , but it d ocs no t by a ny mea ns make it im possi ble, 1 s soo n as t hc convic tion becomes general t hat in ves ti ga t ioll is needed in th is d irection , the force now scattered in all dlrcct ions will ccorue concentrated a t the ri g ht po int , and thus pe r fo rm elli cicn t se rvice in s teadily de ­vcloping f ree Illght,

MAKING BALLOONS.

A conHESPOSDES'l' o f the En glish J[ec1l17 lll c g ives the fo llo w ­in g d escrip t ion of th e p rocess ot manufac t ure of b.il loous, w h ic h m ay interest so me o f our ae ro na u t ica l rea de rs ;

. • In making pass eng er ballo ons, t he si lk is, first of a ll , c u t in 0 s t ri ps a mi sewn toge the r . T Ire g lo be fo rm is then pa r­t ially fil led wi th air a m i vu r u ish cd severa l t im es i a lso tes ted with a ir in sille and a cOl'cr illg of wat er outside. If th e s ilk is lcaky , bnbl llcs a p pear in the water, A \":lll'e is litted tu the to p o f the ha llou ll to a llo w the g as to e~ ea!,e , T he I'a ll'e ro pe passes r il';ht t llro llg h thc con te I' of lho (Mlloon tu the ca r l 'c · n ~a t !t, C;( ron ,.~ Ill'tw(.d e cne 01 VIi, S"S t ile ~ i l k w he n it is fille d " :\11(1 is a Ltliehed to 0. hoo p , froll\ \I' h ieh t,h" ear is s llspend ed . COlli g as lif t,s 'W Ius. p er 1,000 cu l>. ft., ; h y d rogc'n gas l ift s 70 lbs . pCI' 1,00 0 c llb. f t. ' r it e s ma lles t balloon fOl' pa"sen g'cr s is th e 1'3,000 cub. i t. It s w eight I'olllplet c is :?SO Jus. , a nd tlil l

g as \"il ili f t 12 l,iIllI:S'lO illS. = ·[SO Ibs" so th at when inllatcd the balloon has a n :isel' ndi ng pow,'r o f :.? ,'O Ihs. , el(na l to alllan of l UO Ius. and GO Ills . o f stlnd. Wei"h t o f balloou '~ :;O Ill',. ; of Jllan , 1o, Olb s. i of sand , ;' 0 IlJs , i tot a l w<'ight, ,ISO Ibs. "

H arg ra v e ' s E x pcrime n ts. - ,Mr. L a w rellc e I f:lr gra vl', o f Nell' ~ uu t.h \Ya lcs , afte r haVing' huil t SlJme 18 mod el s of l1y ill ~~ lIlaeh iu cs, a ll o ( which lIy, is und erstood to he Ir" pa r ing III huild :L fu ll -Hi ;:ed apparatus t;a pab l,) of , us(a ill ing' hi.; wei ght. 1

If e h as la tc'ly ex pe r illll'n ll'd w ith a glitlin l-( a pp a ra tn s, ha ' cd on the s:lInc benera I 11l'iJ,, 'ip le as L ili e n tha l'~, hu t pro l ide d w ith four win gs s t:t a t a di"dm l a n"lc iuskad of t w o w in" '". T he hcaring s n r faee was It,O Sll.. ft.. ~ :lIld th e we ight :'?;"j I\',s. Th is did no t pro\'(: a S U l:<.: c . ; th" Illa l'hinc wa .-; Ilah"" and uu­ha ndy , and tllrncd O"er w it h the opera to)', who theli reslllll(,,1 h is lahors u pon his" cell u la r kites ," which w cre ill ns l ra l<:d ill A EHOS.\ lJT ICS.

l Ie nuw has one o f th esc whieh I ir'" to wi lll! \I" lft l 0 1 i l ~ .'ta rt ing -po in t. Up on th e st r ing hc in g tied to a s t,,· c in t he g ro u lld , and the kite ra ised . it firs t asc ends a e" rt a in hc i;;ht., 1hL'n :uh 'a m" 's ill to th e wind w hil e th e :< t r ing hlo ll'::I hal: k in l,) a deep bi ,!1lt, upon whkh th' l k ite dl ' s L'l'lld~, an d com(';.; d,,\\ Il t o t,he g ru ll lld :Lt a pu in t h<:lwc;e ll t he s tak e :L nd th e Ild " illa l p llillt uf m is ing , th us [It'r fn rm iug :l fca L sOIJll.: w ha t lik" '; . a.s­llir:ttiOIl .' ·

T he j'Il11,trllctiou o f th e "(,lI l1l,, r k ite h:1S ab o l 'cen Silll[lli . Ii"d . H ) that it ca ll he I'('"di ly fold ell :u lli ca rr i('" a bo u t w h" 1l l) f l:lrg e size.

The la ,'it :lll l'iccs f ro m .\f r. l farg r,, \"( , Wr,,'C r.l: t! ,I~ r l ~c p km . he l' :.?:l , l ::: ~ j I, w hidl i ~ a bou t t.he 0pclli ll" (If , p ri lw ill t h" sll ll l he ll i h em is phere , ~o th at I'll} lIIay I: :-'I',; :t tl) he a r ~ f ill tcr . est illg ex per imen ts t ri eLl hy hi m IIUri llg' till: ( uHdni; ,\.u s t ra li:lu Sll ln ll1er.