307
Chap. 7.]
plan as tliose generally used in engines at this day. This part of the figure(and this alone) in Commandine’s translation of the Spiritalia is not shownin section, but the arrangement of the pipes is precisely as shown in the cut.Now this addition to the discharging pipe could not have been made inthe 16th Century, when the Work feil into the hands of printers and en-gravers, f'or at that time the use of it was not known, while from the smalldimensions figured it could have been of no Service. That it originatedwith Heron and formed a prominent feature in the original figure, is evi-dent from the text: when speaking of the escape of the water from thispart of the machine, he expressly States that it was forced out, in the samemanner as out of a vase or fountain, which he had previously described,by means of compressed air—‘per aerem in ipso compressum.’ & Nothingcan be plainer than this ; for every manufacturer of pumps knows that inthe absence of an air vessel there could have been no air to compress.
It is an intere'sting circumstance in the history of this ancient enginethat the air vessel should have been preserved through so many ages whenits use was not known. While its size was diminished its form was re-tained. It is no wonder that the old copyists considered it an unsightlyand unnecessary enlargement of the discharging pipe, and hence they re-duced it accordingly—certainly the fancy that could add the rectangulartwist to the upper part, would not hesitate to remove the supposed defor-mit.y from the lower one. Some persons, deceived by the imperfect re-presentation, have supposed that such engines were not used in the timeof Heron , and that the figure and description were inserted in his work asmere hints for future mechanicians to improve on ; but the descriptionsufficiently indicates that similar machines were in actual use. b The ma-terials and workmanship of the pumps—metallic pistons and spindle valves,with guards to prevent the latter from opening too far; the mode of form-ing the goose-neck by a kind of swivel joint, somewhat like the Union orcoupling screw ; the application of an air vessel; two pumps forcing waterthrough one pipe, and both worked by a double lever, are proofs that themachine described by Heron was neither an ideal one, nor of recentorigin or use. There are features in it that were very slowly developedby manufacturers in modern times. It is not at all improbable that an-cient engines were equal in effect to the best of ours ; but, whether theywere or not, one thing is certain, that to the ancients belongs the merit ofdiscovering the principles employed in these machines and of applyingthem to practice. It is remarkable too, that fire engines made their firstappearance in Egypt , thus adding another to the numerous obliga.tionsunder which that wonderful country has placed civilized nations in alltimes to come.
Having noticed the use of pumps to extinguish fires in ancient warfare,we may remark that they were also employed in the middle ages, if notbefore, t o promote conflagrations, viz: to lanch streams of Greekfire. Thismysterious substance is represented as a liquid : Beckman says it cer-tainly was one'; and so far from being quenched, its violence was aug-mented by contact with water. It was principally employed in navalcombats, being enclosed in jars that were thrown into the hostile vessels.It was also blown through iron and copper tubes planted on the prows ofgalleys and fancifully shaped like the mouths of animals, which seemed tovomit streams of liquid fire. Th'ere is among the figures of war machinesm the old German translation ofVegetiüs already mentioned, one that
a Spiritalia, p. 70.
'' Siphones autem quibus utuntur ad incendia hoc modo construuntur.—Ibid.