26 



KNOWLEDGE & SCIENTIFIC NEWS. 



[February, ii/O?- 



If a t;i\'fii voliinu' of :iir \n- (lisplact'd and tin- space 

 filled by a vessel iiillated with some suljstanee lijihter 

 than air, such as Iiydroijen, coal gfas, steam, or air 

 rendered less dense by beins^ heated, then, if tlic con- 

 taining vessel is not too heavy the whole will rise in 

 tlie air. This is in obidii'nce to well-Unowii laws. '1 he 

 heavier particles of air will slip under the lii^hter Ixuly 

 and buov it up, just as water when poured into a basin 

 would slip under and buoy up a cork lyini; in the basin. 

 That air has definite weight can easily be proved by 

 carefully wei.y:hint,'- a bottle which has been exhausted of 

 air, and weii;hintr it a.ij'ain when air is admitted to it. 

 In this way air is found to weifrh .075 lb. per cubic 

 foot, or 1,000 cubic feet will wcis:h 75 lbs. 



Hydrogen gas can l>c weighed in the same manner, 

 and i.s found to be .005 lb. per cubic foot, or 5 lbs. for 

 1. 000 cubic feet. Coal gas varies, but may average 

 about 35 to .JO lbs. per 1,000 cubic feet. Steam, which 

 has actually been applied to ballooning, varies accord- 

 ing to its temperature*. .As regards heated air, what is 

 known as Ch.irles's law shows that a given volume, 

 under constant pressure, increases with temperature 

 .00367 times its bulk per degree Centigrade, or .002 

 Mtt) pei" degree Fahrenheit. If, then, the air in a 

 balloon can be raised by loo" F., one-fifth of its weight 

 will be exj>elled; that is, each cubic foot will then weigh 

 f of .075, or .06 lb., or 1,000 cubic feet will weigh 60 

 lbs. instead of 75. 



The.se principles are often overlooked by unscientific 

 inventors, who sugg-est adding a small balloon to aid 

 in lifting their apparatus, or who anticipate a hope of 

 finding a gas lighter than hydrogen. 



One F. Lana, in 1670, was probably the first to 

 suggest the idea of a machine on this principle, but his 

 suggestion was to exhaust the air from large copper 

 globes, ignoring the practical fact that the pres.sure of 

 the atmosphere would crush in any such vessel as soon 

 as a very small quantity of air had been extracted from 

 it. 



The second methcwl, though interesting as a specula- 

 tive suggestion, seems hardly likely to prove of prac- 

 tical utility, for a man-carrying machine. 



Rocket.s are wcW known. They are practically useful 

 for many special purposes, but are extremely wasteful 

 of fuel, and, therefore, short-lived. Steam jets striking 

 downwards have been suggested. 



Mr. H. Wilde, F.R.S., conducted a number of ex- 

 periments at one time* in order to ascertain what force 

 could be practically applied with this idea. He tried 

 high pressure steam and compressed air through orifices 

 of manv various forms, also explosions of gas mixed 

 with air and ignited by electric sparks He, however, 

 sums up the whole matter by saying : " The results of 

 all these experiments on the discharge of elastic fluids, 

 made with a view to the possibilities of aerial loco- 

 motion, were purely negative, and proved decisiyely 

 that the solution of the problem was not to be found in 

 that direction." It occurs to me, though 1 have not 

 actually tried the experiment, that liquid air might be 

 used in this connection. A vessel of liquid air in 

 ordinary atmospheric circumstances is practically 

 equivalent to a vessel of water placed in the middle of 

 a furnace. The liquid air in the one case and the 

 water in the other are boiling hard and rapidly 

 evaporating into air or steam respectively. So that by 

 employing this method we practically have a steam 

 boiler exposed to a comparatively very high temperature 

 (that is the difference between that of the liquid and 



* " On Animal Locomotion." by Henry Wilde, F.R.S. Vol. 

 xliv. No. II. of the "Memoirs of the Manchester Literarj' and 

 Philosophical Society." 1900. 



that of the surroimding atmosphere), yet without any 

 fuel or apparatus for binning fuel. .\ great pressure 

 may thus be obtained with but little weight, and it 

 could, therefore, be made to a.sccnd. It is true that 

 this action may be very wasteful and would not last 

 long. Still, as an experiment, it might be interesting 

 to see a vessel rise in the air by this novel means. 



It may be added th:it though a continuous stream 

 issuing from a jet may, theoretically, be wasteful of 

 power, it would probably not Ik- dillicult to make the 

 jet intermittent, or, by progressing rajiidly in a hori- 

 zontal direction, to cause it to act continu.illy on fresh 

 air. 



The third principle, which promises the most practi- 

 cal results, and is a much larger subject, wc must leave 

 for a future article. 



(7V) he colli hiucd.) 



Qvieei\'s College Horn. 



In the Buttery of Queen's College, Oxford, is preserved 

 one of the city's greatest curiosities. It is an old 

 drinking cup presented to the College by Philipjia, 

 Consort to Edward III., more than five hundred years 

 ago, from whom it took its name. In shape it re- 

 sembles a horn; it is made of polished horn, brown in 

 colour, and richly decorated in silver-gilt. It is one 

 foot eight inches high, and the outer curve from the 



SUetcUfil hi/Rtiiry K. Crapper, Qufcn's CoUcga Lodge. 

 Horn in the Buttery, Queen's College, Oxford. 



extreme points is forty-one inches. It will hold two 

 quarts. 



On the lid is a silver eagle of curious workmanship, 

 and the whole is supported by eagles' claws. 



An eagle was the crest of the founder of the College, 

 ■vobert de Eglesfeld, Confessor to Oueen Philippa. 

 This cup is still used on " Gaudy " day, and is handed 

 round after dinner. The contents consist of 

 " Chancellor," a strong beer brewed bv the College — 

 sherry and brandy flavoured with pine-apple. 



