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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



to other stars, I ventured to make a prediction 

 as to the result which he would obtain whenso- 

 ever he should apply it to five stars of the seven 

 forming the so-called Plough. I had found rea- 

 son to feel assured that these five form a system 

 drifting all together amid stellar space. Satisfied 

 for my own part as to the validity of the evidence, 

 I submitted it to Sir J. Herschel, who was struck 

 by its force. The apparent drift of those stars 

 was, of course, a thwart-drift; but if they really 

 were drifting in space, then their motions in the 

 line of sight must of necessity be alike. My predic- 

 tion, then, was that whensoever Mr. Huggins ap- 

 plied to those stars the new method he would find 

 them either all receding at the same rate, or all 

 approaching at the same rate, or else that all 

 alike failed to give any evidence at all either of 

 recession or approach. I had indicated the five 

 in the first edition of my "Other Worlds" — to 

 wit, the stars of the Plough, omitting the nearest 

 "pointer " to the pole and the star marking the 

 third horse (or the tip of the Great Bear's tail). 

 So soon as Huggins's new telescope and its spec- 

 troscopic adjuncts were in working order, he re- 

 examined Sirius, determined the motions of other 

 stars, and, at last, on one suitable evening he 

 tested the stars of the Plough. He began with 

 the nearest pointer, and found that star swiftly 

 approaching the earth. He turned to the other 

 pointer, and found it rapidly receding fiom the 

 earth. Being under the impression that my five 

 included both pointers, he concluded that my pre- 

 diction had utterly failed, and so went on with his 

 observations altogether unprejudiced in its favor, 

 to say the least. The next star of the seven he 

 found to be receding at the same rate as the sec- 

 ond pointer ; the next at the same rate ; the next, 

 and the next, receding still at the same rate, and 

 lastly the seventh receding at a different rate. 

 Here, then, were five stars, all receding at a com- 

 mon rate, and of the other two one receding at 

 a different rate, the other swiftly approaching. 

 Turning next to the work containing my predic- 

 tion, Huggins found that the five stars thus re- 

 ceding at a common rate were the five whose 

 community of motion I had indicated two years 

 before. Thus the first prediction ever made re- 

 specting the motions of the so-called fixed stars 

 was not wanting in success. I would venture to 

 add that the theory of star-drift, on the strength 

 of which the prediction was made, was effectively 

 confirmed by the result. 



The next application of the new method was 

 one of singular interest. I believe it was Mr. 

 Lockyer who first thought of applying the method 



to measure the rate of solar hurricanes as well 

 as the velocities of the up-rush and down-rush of 

 vaporous matter in the atmosphere of the sun. 

 Another spectroscopic method had enabled as- 

 tronomers to watch the rush of glowing matter 

 from the edge of the sun, by observing the col- 

 ored flames and their motions ; but by the new- 

 method it was possible to determine whether 

 the flames at the edge were swept by solar cy- 

 clones carrying them from or toward the eye of 

 the terrestrial observer, and also to determine 

 whether glowing vapors over the middle of the 

 visible disk were subject to motion of up-rush, 

 which of course would carry them toward the eye, 

 or of down-rush, which would carry them from 

 the eye. The result of observations directed to 

 this end was to show that at least during the 

 time when the sun is most spotted, solar hurri- 

 canes of tremendous violence take place, while 

 the up-rushing and down-rushing motions of solar 

 matter sometimes attain a velocity of more than 

 100 miles per second. 



It was this success on the part of an English 

 spectroscopist which caused the attack on the 

 new method against which it has but recently 

 been successfully defended, at least in the eyes 

 of those who are satisfied only by experimental 

 tests of the validity of a process. The Padre 

 Secchi had failed, as we have seen, to recognize 

 motions of recession and approach among the 

 stars by the new method. But he had taken 

 solar observation by spectroscopic methods under 

 his special charge, and therefore when the new 

 results reached his ears he felt bound to confirm 

 or invalidate them. He believed that the appar- 

 ent displacement of dark lines in the solar spec- 

 trum might be due to the heat of the sun causins 

 changes in the delicate adjustments of the instru- 

 ment — a cause of error against which precautions 

 are certainly very necessary. He satisfied him- 

 self that when sufficient precautions are taken no 

 displacements take place such as Lockyer, Young, 

 and others, claimed to have seen. But he sub- 

 mitted the matter to a further test. As the sun 

 is spinning swiftly on his axis, his mighty equa- 

 tor, more than 2,500,000 miles in girth, circling 

 once round in about twenty-four days, it is clear 

 that on one side the sun's surface is swiftly 

 moving toward, and on the other side as swiftly 

 moving from, the observer. By some amazing 

 miscalculation Secchi made the rate of this mo- 

 tion twenty miles per second, so that the sum of 

 the two motions in opposite directions would 

 equal forty miles per second. He considered 

 that he ought to be able by the new method, if 



