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SCIENCE. 



[N. S. Vol. V. No. 125. 



being are so far hidden from mortal eyes as 

 in the depths of the universe. But, with- 

 out declaring its positive certainty, it must 

 be said that the conclusion seems unavoid- 

 able that a number of stars are moving with 

 a speed such that the attraction of all the 

 bodies of the universe could never stop 

 them. One such case is that of Arcturus, 

 the bright reddish star familiar to mankind 

 since the days of Job, and visible near the 

 zenith on the clear evenings of May and 

 June. Yet another case is that of a star 

 known in astronomical noiaenclature as 

 1830 Groombridge, which exceeds all others 

 in its angular proper motion, as seen from 

 the earth. We should naturally suppose 

 that it seems to move so fast because it 

 is near us. But the best measurements 

 of its parallax seem to show that it can 

 scarcely be less than two million times the 

 distance of the earth from the sun, while it 

 may be much greater. Accepting this re- 

 sult, its velocity cannot be much less than 

 200 miles per second, and may be much more. 

 With this speed it would make the circuit of 

 our globe in two minutes, and had it gone 

 round and round in our latitudes we should 

 have seen it fly past us a number of times 

 since I commenced this discourse. It would 

 make the journey from the earth to the sun 

 in five days. If it is now near the center 

 of our system it would probably reach its 

 confines in a million of years. So far as 

 our knowledge of nature goes, there is no 

 force in nature which would ever have set it 

 in motion, and no force which can ever stop 

 it. What, then, was the history of this star, 

 and if there are planets circulating around, 

 what the experience of beings who may have 

 lived on those planets during the ages which 

 geologists and naturalists assure us our earth 

 has existed ? Did they see, at night, only a 

 black and starless heaven? Was there a time 

 when, in that heaven, a small faint patch of 

 light began gradually to appear ? Did that 

 patch of light grow larger and larger as mil- 



lion after million of years elapsed ? Did it at 

 last fill the heavens and break up into 

 constellations as we now see them? As 

 millions more of years elapse will the con- 

 stellations gather together in the opposite 

 quarter, and gradually diminish to a patch 

 of light as the star pursues its irresistible 

 course of 200 miles per second through the 

 wilderness of space, leaving our universe 

 farther and farther behind it, until it is lost 

 in the distance? If the conceptions of 

 modern science are to be considered as 

 good for all time, a point on which I con- 

 fess to a large measure of scepticism, then 

 these questions must be answered in the 

 aflBrmative. 



Intimately associated with these problems 

 is that of the duration of the universe in 

 time. The modern discovery of the con- 

 servation of energy has raised the question 

 of the period during which our sun has 

 existed and may continue in the future to- 

 give us light and heat. Modern science 

 tells us that the quantity of light and heat 

 which can be stored in it is necessarily 

 limited, and that, when radiated as the sun 

 radiates, the supply must in time be ex- 

 hausted. A very simple calculation shows- 

 that were there no source of supply the sun 

 would be cooled off in three or four thou- 

 sand years. Whence, then, comes the sup- 

 ply? During the past thirty years the source 

 has been sought for in a hypothetical con- 

 traction of the sun itself. True, this contrac- 

 tion is too small to be observed; several 

 thousand years must elapse before it can 

 be measurable with our instruments. Grant- 

 ing that this is and always has been the 

 sole source of supply, a simple calculation 

 shows that the sun could scarcely have 

 been giving its present amount of heat for 

 more than twenty or thirty millions of 

 years. Before that time the earth and the 

 sun must have formed one body, a great 

 nebula, by the condensation of which both 

 are supposed to have been formed. But 



