514 Siphons. [Book V.
to call man’s attention to this department of knowledge, and to inducehim to cultivate it.
Sources of hydratdic contrivances and of mechanical movements areendless in nature ; and if machinists would but study in her school, shewould lead them to the adoption of the best principles, and the mostsuitable modifications of them in every possible contingency.
C H A P T E R VI.
Siphons —Mode of charging them—Principle on which their action depends—Cohesion of liquids—Siphons act in vacuo—Variety of siphons—Their antiquity—Of Eastern origin—Portrayed in the tombsat Thebes —Mixed wines—Siphons in ancient Egyptian kitchens—Probably used at the feast at Cana—Their application by old jugglers—Siphons from Heron’s Spiritalia—Tricks with liquids of dilFerentspecific gravities—Fresh water dipped from the surface of the sea—Figures of Tantalus’ cups—Tricksof old publicans—Magic pitcber—Goblet for unwelcome visiters—Tartar necromancy with cups—Romanbaths—Siphons used by the ancients for tasting wine—Siphons, A.D. 1511—Figures of modern siphons—Sucking tube—Valve siphon—Tin plate—Wirtemburg siphon—Argand’s siphon—Chemists’siphons—Siphons by the author—Wacer conveyed over extensive grounds by siphons—Limit of the applicationof siphons known to ancient Plurabers—Error of Porta and olher writers respecting siphons—Decaus—Siphons for discharging liquids at the bend—Ram siphon.
The siphon , or as it is sometimes named the crane, is in its simplestform merely a tube bent so as to resemble an inverted letter Uor V; andis employed to transfer liquids from one level to a lower one, in cireum-stances where natural or artificial obstructions prevent a straighi pipefrom being used ; as when rocks or rising grounds intervene between aspring and the place where the water is required, or when the contentsof casks and other vessels are to be withdrawn without making openingsfor the purpose in their bottom or sides. Thus farmers occasionally havewater conveyed over hills to supply their barn-yards and dwellings; andportable siphons are in constant requisition with oil and liquor merchants,chemists and distillers. The two branches of a tube that constitute asiphon are commonly of unequal lengths, and named legs ; the “ short’' orreceiving leg, and the “ long” or discharging one. The highest part wherethe legs are united is known as the apex or bend.
As liquids are raised in siphons by atmospheric pressure, the perpen-dicular length of the short leg, like the suction pipe of a pump, shouldnever exceed 25 or 28 feet. To put siphons in Operation, the air withinthem must be first expelled. Small ones are sometimes inverted andfilled with a portion of the fluid to be decanted, but more frequently theliquid is drawn through the tube by sucking. Other devices for chargingthem will be noticed farther on.
The action of a siphon does not depend upon any inequality of atmo-spheric pressure, as some writers on natural philosophy have inadvertentlyintimated. In one populär work, it is said, “ the pressure of the air ismore diminished and in another, more “ weakened or abated” over thedischarging than over the receiving orifice; whereas, philosophicallyspeaking, the reverse is the fact: for as the discharging end is nearer theearth, a Reeper and consequently heavier column of atmosphere rests over