Flotation Of Spiders

In an interesting communication te Knowledge on "Spiders, " the Rev. Samuel Barber disensses at sonie length the phenomenon of the flotation line, p,nd its method of attachment, which is the foundation of the spider's web. Is it not evident, asks the reverend gentleman, that air - and probably at a high temperature - must be inclosed within the ineshes of the substance f orm ing the line when it passes from the spinnerets into the atmosphere? The creature with this substauce lifts it into the air. It has been usual to explain the aseent by the kiro principie - namely, the mechanical force of the contiguous atmosphere - but air moveuieuts, especially on a small scale, are so capricious and uncontrollable that without a directive force the phenoniena seem quite inexplicable. In support of this theory of a direct propelling force Mr. Barber gives soiue of his own observations. Writing one day with two sheets of quarto before him, he saw a small spider on the paper, and in order to test its power of passing throngh the air he held one of the sheets of paper about a toot froia that on which the oreature was running. It ascended to the edge and vauished, but in a moment it lauded upon the other sheet throngh midair in a horizontal directiou, and piuktd up tha thread as it advanoed. In this oase there was no air moveiuttnt to facilítate, nor any time to throwaline upwaid, whioh indeed would uot have solved the diiïiculty. On anot.her occasion, at a dluJuei party in Kent, four candlcs wa lighted on the tab! e, when a thread was suen to be Rtiung trom the tip of (me of the lighted candles and attached to anothor about a yard off," and all the four lights were oonneoted in this way, aud that by a web drawn quite tight. The only explanation which Mr. Bai-ber can miggest for this remarkable oocurrenco is that the sijinner was suspended at iirst by a vertical line from above and thus swayed itself to and fro from tip to tip of the candles. It was certain the spider could not have ascended from thetable, and it wasequally certain that aerial flotation of the line from a fixed poiut was impossible, as it involved floating in four opposite directionH. The rapidity with wliich the initial movements in forming a web are made cannot ba reconciled with any theory of a simple atmospheric convection, and propulsión appears the only explanation.