Mr. Glaisher remarks of his twelfth ascent that the anemo-
meters at Greenwich and elsewhere give no idea of the real velocity of the upper currents of wind. Last year he said that Mr. &swell made a journey of seventy miles in sixty- five minutes, when the anemometer at Greenwich only showed a velocity of fourteen miles an hour. On this occasion Mr. Glaisher moved at the rate of about sixteen miles an hour, when the Greenwich anemometer gave a velocity of only two miles an hour. It is clear that the upper currents of wind move far more rapidly than the lower, and sometimes, as we know, in different directions. Probably the lower parts of the atmosphere being much the denser, the rarefaction and ,condensation which go on there are much less in degree than in the upper and thinner strata, just as the currents in the sea, which arise from exactly the same causes, but in a denser substance, are meal slighter in velocity than the similar cur- rents, called winds, in the atmosphere.
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