192

Ancient Experiments on Air.

[Book II.

that air was a frequent subject of investigation with their philosophers,and that its influence in some natural phenomena was well understood.Thus Diogenes of Apollonia , the disciple and successor of Anaximenes ,reasoned on its condensation and rarefaction. According to Aristotle , Em-pedocles accounted for respiration in animals by the weight of the air,which said he, “ by its pressure insinuates itself with force into the lungs.”Plutarch expresses in the very same terms, the Sentiments of Asclepiades ,representing him among other things as saying that the external air, “ lyits weight, opened its way with force into the breast.” Lucretius , in ex-plaining the property of the loadstone in drawing iron, observed that itrepelled the intervening air betwixt itself and the iron, thus forming avacuum, when the iron is “ pushed on by the air behind it.” Plutarch was of the same opinion.“ Vitruvius speaks of the pressure of air, Arch.book viii, cap. 3. When Flaminius , during the celebration of the Isthmi-an games, proclaimed liberty to the Greeks, the shout which the peoplegave in the transport of their joy was so great, that some crows, which hap-pened to be then flying over their heads, feil down into the theatre. Plu­ tarch among other explanations of the phenomenon, suggests, that the“ sound of so many voices being violently strong, the parts of the air wereseparated by it, and a void left which afforded the birds no support.” b

But if the ancients did not detect or comprehend the direct pressure ofthe atmosphere, they were not ignorant of its effects, or of the means ofexciting it. They in fact employed air in many of their devices as success-fully as the moderns. They compressed it in air guns, and weighed it inbladders ; its elasticity produced continuous jets in their fountains andforce purnps, in the same manner as in ours ; by its pressure, they raisedwater in syringes and pumps, and transferred it through siphons, preciselyas we do; they excluded its pressure from the upper surface of waterin their sprinkling pots, and admitted it to empty fhem, as in the modernliquor merchant’s taster. That they had condensing air pumps is evidentfrom the wind guns of Ctesibius , as well as others described by Vitruvius ,b. x, cap. 13 ; and it is probable that they employed airinnumerous othermachines and for other purposes, but of which, from the loss of theirwritings, no account has been preserved. See Vitruvius , book x, cap. 1,where some are referred to, and Pliny Nat. Hist, book xix, cap. 4.

It would be in vain to attempt to discover the origin of devices forraising liquids by the pressure of the atmosphere, for it would require aknowledge of man and of the state of the arts, in those remote ages ofwhich no record is extant. That machines for the purpose were madelong before the commencement of history is certain, for recent discov-eries have brought to light the highly interesting fact, that siphons wereknown in Egypt 1450 years before our era, i. e. 3290 years ago ! Atwhich period too they seem to have been in more common use in thatcountry, than they are at this day with us. [See Book V, for an accountof these instruments.]

The retention of water in inverted vessels while air is excluded fromthem, could not have escaped observation in the rüdest ages. Long erenatural phenomena had awakened curiosity in the human mind, or rousedthe spirit of philosophical inquiry and research, it must have been noticed.When a person immerses a bücket in a reservoir and raises it in an in-verted position, he soon becomes sensible that it is not the weight of thevessel merely which he has to overcome, but also that of the water withm

a Duten’s Inquiry into the Origin of the Discoveries attributed to the Moderne. Lon..1769, pp. 186, 187 203. b Life of Flaminius.