Year: 1860

Encke's comet, which revolves about the sun in three and half years, has been oo- served to complete its revolution in a con stantly shortening period, showing that It Is beino drawn inward toward the sum- 1hlS fact has led to the general conclusion by as tronomers that the planets are moving Tn re- sistless medium, far more attenuated than our atmosphere, but still sufficient to affect then motions. If this be so, 1t follows by strict necessity that our earth and its sister orbs are all winding spiraIy toward the sun, and that they must eventually strike against 1t and be- come incorporated with its mass. The tune required for this purpose belongs to those Tn, conceivable periods with which geology and astronomy have to deal. The resisting medl- uln is so exceedingly attenuated that 1t eXerts but slight influence on the comets, winch are themselves masses of the very thinest yapor, and its influence would of course be very much less on the dense matter ot the planets Astronomical observations with all then wonderful delicacy have yet failed to detect the slightest progressive shortening in the periods of revolution of any of the planets. It is curious, however, to note the multiplied obstacles which prevent the perception ot this fact. if 1t does exist. All the measures of these revolutions are shortening with the revolutions themselves. If we begin, for in- stance. with the earth, the problem IS to as certain whether the time occupied by the earth in its journey around the sun IS gradu- ally becoming shorter. The first plan that suggests itself is to compare this with the rotation of the earth on its axis, to see whether the year occupies the same number of days and hours and seconds that it did in former times. But if the earth IS gradually cooling. it is contracting in size, and its rota- ton or its axis is becoming more rapid. In other words. the day IS shortening with the wear; and if the measure shrinks ust in pro- l portion to the thing measured, we cannot tell whether the latter is becoming shorter or not. ] Ii we take the time of the revolutions of 1 the moon around the earth as q standard, the same resisting medium would draw the moon ! toward the earth, and shorten the month also with the year. If we resort even to the less satisfactory measure of the suns rotation on l his axis. his bulk is also diminishing by the radiation of his heat, and the period of his re- 1 tation is, consequently. becoming shorter. ] In brief from the two cases ofraGlati0n and ! the resisting medium all tho times and dis tanccs which could be used to measure the earh's distance from the sun Cor the period i of its annual rcyolUt;9n) are shortening to- ! gether So that the differences in the extent l of these several contradictions are the only

 means left for detecting by observation on the approach of the etrh 10 the sun. if such ap- proach is really taking place. These differ

 ences would doubtless reveal themselves ir

 the course of generations to refined astronom- 1 ical observations.

 1.-the cuth and the sun arc gradually be-

 coming cold, this winding of the earth toward

 the sun would tend to keepup its warmth

 and it may 5a a wise provision ior prolonging

 by some millions of years the continuance ol

 animal life upon our globe. But this period

 must come to a close tor ifhere is a resisting

 medium prevailing the space between q. and

 the sun, the final destiny of the earth is {,

 curve gradually forward t.L, with velocity

 hundreds of times greater than that of can

 non ball. it dashes itself with an awiully sub lime crash into the mass oi the sun.

 Scientific American.