^•eight because of Its large iliameter. A.itl 

 tor Lbis reason, allow no piirts wiih 

 large (iinieiieions on wliich the steam 

 jirc's^fcure conies, in this latter cas,e oiiiy 

 a light hall is required to surround tlie 

 Jlues, to confine the heat to its v^^^- 

 And it would r€<iuire a greater internal 

 fiirnin to burst these tubes ihati external 

 pressure to L'^Jlla!)'^e theni. Now in tins 

 case, to secure the greatest heating si:r- 

 face with the sinallest water space, the 

 flues containing the water should have 

 as sii;all a diameter as possibie, because 

 if we lessen their diameters one-half, we 

 will lessen the amount of witer tluy 

 coniain lo ont-founh that of the for.i er 

 amount, and only lessen their hearing 

 surface one-half. They may be made 

 much light»^r with suilicient strength to 

 stand the strain, because of their smalier 

 diameters. 



A.~Mr. B, v/hile all these air-ships we 

 have been di*c^J^sing, may be satisfactory 

 for slow velocities, we cannot satisfy our 

 selves without hiulier velocities. We 

 should travel several hutidied miles per 

 hour, to carry our mails, if not pass- 

 engers. Are thera not fair prospects 

 that we will soon a'lvance to tiiis point? 



E — Mr, A, You h:>\-f j)robabiy observed 

 the flight of dill'erent birds— we take the 

 crane and the duck for illiistraliuii. Y"u 

 will observe the crane is possessed of 

 wings, or sustaining mechanism, with 

 very large surfaces, in comparison to its 

 weight, to move against the air. Due 

 the reverse is ilie case with thv' duck. 

 Now the condition of ths- crane with the 

 large surface of its sustaining api)aratus, 

 means tlie greatest economy of ttie 

 energy stored within its body, because 

 of the great areas cf its wing moving 

 slowly against the air, being an exact 

 representation of the enlarged areas of the 

 Bustainiug surfaces of air-ships. Tht^ duck 

 pOi-sesses on the contrary a \ery heavy 

 boiiy in compaiison to the area of its wings, 

 and you will observe during its liight that 

 its wings mo-' e against the air at a very 

 rapid rate, in order to sustain the e.)m- 

 paratively great weight of its body. This 

 means a great wast- of its stored energy, 

 and is a represent." lion of the sustain- 

 inj; surfaces of air-ships with snndl aiees. 

 Now Mr. A, it is not diflicult to i)bserve 

 tJie difference in the Higbt of these two 

 binla. The flight of the crane being ex- 

 cedingly slow and awkward, and the 

 reverse being the case wirh the duck. 

 Now while the duck during its (light, 

 loses far more energy per second, to 

 each pound weight of its body than the 

 crane, it has the conditions jiresent to 

 enable it to reach a far greater velocity ; 

 E-ad these conditions could not be present 

 without this heavy loss of energy. 



A^Mr. B, what are these conditions 



ih-xt enable the duck to reach its rapid 

 a>'-e«s>ion and flight? 



li— Mr. A, you will observe the duck to 

 be more compact than the crane; this 

 is a condition suitable to rapid flight. 

 But most important of all is the fact, 

 tiiat it possesses the possibility of with- 

 drawing from its source a far greater 

 amount of energy in a given time, to 

 each pound weight of its body than that 

 of the crane. And in regard to the mech- 

 anism of the duck, which this energy 

 must actuate to bring about the rapid 

 ascension and horizontal flight, it is 

 undoubtedly a fact that the rapid flight 

 is brought about by sucli a motion of 

 tlie wings that they force the air more 

 nearly directly backward, and at a more 

 rcitiid rate tlian that of the crane. Ani 

 the smali sustaining surfaces or wings of 

 the duck moving downward against the 

 air at a rapid rate, have a tendency when 

 they have released the weight of the duck 

 from its place of rest, to cause it to 

 aNcen«i wish a bound similar to that of 

 a sky rocket, and for a similar reason; 

 wliile the crane with its enlarged sustain- 

 ing surfaces moving downward against 

 the air at a slow vcloity, is incapable of ■ 

 bringing about such a result. 



A- VUit Mr. 15 what has all this about 

 the duck and the crane to do with air-ships? 



B— It is my object to compare the build 

 and proportions of air-shiiis to the build 

 and propoitinis of the duck and crane. 

 You will ob.-e-vethe comparatively bulky, 

 awkward and slow luofioued air-ship 

 with large sustaining? surfaces representing 

 great economy in power, to be a repre- 

 sentation of, and is built on the plan of 

 the crane, lint Mr. A, if we hope to 

 re.ich any great ve hjcilies with our air-ship 

 we must have the conditions of the duck. 

 We must have the conditions present 

 from which we can withdraw an enor- 

 mous amount of energy in a short per- 

 iod of lime. Yi»u understand we require 

 a Very large nnmber of foot pounds of 

 energy per second to each pound weight 

 of the ship, in onler to handle it quickly. 

 The shir, must, like the duck or sky- 

 rocket be capable of rising from the 

 earth with a binind. It must not consume 

 an hour in rising a thousand feet high, 

 but must quickly rise to an altitude 

 from which it takes its horizontal flight, for 

 the obje.;t of this ship is to travel the 

 greatest possible distance in a given time. 

 And its rapid ascension is required for 

 the reason th t it must land frequently 

 to renew its store of energy. When we 

 secure our energy and bring about the 

 conditions in order that it may be used 

 rapidly as desired, Vire willj like the duck, 

 be able to ascend and travel horizontally 

 with great velocity. But remember, the 

 greatei portion of the energy, as in the 



