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air。 Wait for some little better cylinders of oxygen and an improved foot…warmer； and a future Coxwell will go aloft and see； but as to an upper sea； it is truly there； and we may visit and view its sun…lit tossing billows stretching out to a limitless horizon at such times as the nether world is shrouded in densest gloom。 Bacon's method of reaching such an upper sea as he postulated was； as we have said； by a hollow globe。
〃The machine must be a large hollow globe； of copper or other suitable metal； wrought extremely thin so as to have it as light as possible；〃 and 〃it must be filled with ethereal air or liquid fire。〃 This was written in the thirteenth century； and it is scarcely edifying to find four hundred years after this the Jesuit Father Lana； who contrived to make his name live in history as a theoriser in aeronautics； arrogating to himself the bold conception of the English Friar； with certain unfortunate differences； however； which in fairness we must here clearly point out。 Lana proclaimed his speculations standing on a giant's shoulders。 Torricelli； with his closed bent tube； had just shown the world how heavily the air lies above us。 It then required little mathematical skill to calculate what would be the lifting power of any vessel void of air on the earth's surface。 Thus Lana proposed the construction of an air ship which possibly because of its picturesquesness has won him notoriety。 But it was a fraud。 We have but to conceive a dainty boat in which the aeronaut would sit at ease handling a little rudder and a simple sail。 These； though a schoolboy would have known better； he thought would guide his vessel when in the air。
So much has been claimed for Father Lana and his mathematical and other attainments that it seems only right to insist on the weakness of his reasoning。 An air ship simply drifting with the wind is incapable of altering its course in the slightest degree by either sail or rudder。 It is simply like a log borne along in a torrent； but to compare such a log properly with the air ship we must conceive it WHOLLY submerged in the water and having no sail or other appendage projecting into the air； which would； of course； introduce other conditions。 If； however； a man were to sit astride of the log and begin to propel it so that it travels either faster or slower than the stream； then in that case； either by paddle or rudder； the log could be guided； and the same might be said of Lana's air boat if only he had thought of some adequate paddle； fan； or other propeller。 But he did not。 One further explanatory sentence may here be needed； for we hear of balloons which are capable of being guided to a small extent by sail and rudder。 In these cases； however； the rudder is a guide rope trailing on earth or sea； so introducing a fresh element and fresh conditions which are easy to explain。
Suppose a free balloon drifting down the wind to have a sail suddenly hoisted on one side； what happens？ The balloon will simply swing till this sail is in front； and thus continue its straightforward course。 Suppose； however； that as soon as the side sail is hoisted a trail rope is also dropped aft from a spar in the rigging。 The tendency of the sail to fly round in front is now checked by the dragging rope； and it is constrained to remain slanting at an angle on one side； at the same time the rate of the balloon is reduced by the dragging rope； so that it travels slower than the wind； which； now acting on its slant sail； imparts a certain sidelong motion much as it does in the case of a sailing boat。
Lana having in imagination built his ship； proceeds to make it float up into space； for which purpose he proposes four thin copper globes exhausted of air。 Had this last been his own idea we might have pardoned him。 We have； however； pointed out that it was not； and we must further point out that in copying his great predecessor he fails to see that he would lose enormous advantage by using four globes instead of one。 But； beyond all； he failed to see what the master genius of Bacon saw clearlythat his thin globes when exhausted must infallibly collapse by virtue of that very pressure of the air which he sought to make use of。
It cannot be too strongly insisted on that if the too much belauded speculations of Lana have any value at all it is that they throw into stronger contrast the wonderful insight of the philosopher who so long preceded him。 By sheer genius Bacon had foreseen that the emptied globe must be filled with SOMETHING； and for this something he suggests 〃ethereal air〃 or 〃liquid fire；〃 neither of which； we contend； were empty terms。 With Bacon's knowledge of experimental chemistry it is a question； and a most interesting one； whether he had not in his mind those two actual principles respectively of gas and air rarefied by heat on which we launch our balloons into space to…day。
Early progress in any art or science is commonly intermittent。 It was so in the story of aeronautics。 Advance was like that of the incoming tide； throwing an occasional wave far in front of its rising flood。 It was a phenomenal wave that bore Roger Bacon and left his mark on the sand where none other approached for centuries。 In those centuries men were either too priest…ridden to lend an ear to Science； or； like children； followed only the Will…o'…the…Wisp floating above the quagmire which held them fast。 They ran after the stone that was to turn all to gold； or the elixir that should conquer death； or the signs in the heavens that should foretell their destinies； and the taint of this may be traced even when the dark period that followed was clearing away。 Four hundred years after Roger's death； his illustrious namesake； Francis Bacon； was formulating his Inductive Philosophy； and with complete cock…sureness was teaching mankind all about everything。 Let us look at some of his utterances which may help to throw light on the way he regarded the problem we are dealing with。
〃It is reported；〃 Francis Bacon writes； 〃that the Leucacians in ancient time did use to precipitate a man from a high cliffe into the sea； tying about him； with strings； at some distance； many great fowles； and fixing unto his body divers feathers； spread； to breake the fall。 Certainly many birds of good wing （as Kites and the like） would beare up a good weight as they flie。 And spreading of feathers； thin and close； and in great breadth； will likewise beare up a great weight； being even laid without tilting upon the sides。 The further extension of this experiment of flying may be thought upon。〃
To say the least； this is hardly mechanical。 But let us next follow the philosopher into the domain of Physics。 Referring to a strange assertion； that 〃salt water will dissolve salt put into it in less time than fresh water will dissolve it；〃 he is at once ready with an explanation to fit the case。 〃The salt；〃 he says； 〃in the precedent water doth by similitude of substance draw the salt new put in unto it。〃 Again； in his finding； well water is warmer in winter than summer； and 〃the cause is the subterranean heat which shut close in （as in winter） is the more； but if it perspire （as it doth in summer） it is the le