January 23, 1903.] 



SCIENCE. 



125 



urably distant. A remarkable fact is that 

 these conclusions coincide with that which 

 we draw from the minuteness of the proper 

 motions. Rigel has no motion that has 

 certainly been shown by more than a cen- 

 tury of observation, and it is not certain 

 that Canopus has either. From this alone 

 we may conclude, with a high degree of 

 probability, that the distance of each is 

 immeasm-ably great. AVe may say with 

 certainty that the brightness of each is 

 thousands of times that of the sun and with 

 a high degree of probability, that it is hun- 

 dreds of thousands of times. On the other 

 hand, there are stars comparatively near 

 us of which the light is not the hundredth 

 part that of the sun. 



The universe may be a unit in two ways. 

 One is that unity of structure to which our 

 attention has just been directed. This 

 might subsist forever without one body 

 infliiencing another. The other form of 

 unity leads us to view the universe as an 

 organism. It is such by mutual action go- 

 ing on between its bodies. A few years 

 ago we could hardly suppose or imagine 

 that any other agents than gravitation and 

 light could possibly pass through spaces 

 so immense as those which separate the 

 stars. 



The most remarkable and hopeful char- 

 acteristic of the unity of the universe is 

 the evidence which is being gathered that 

 there are other agencies whose exact nature 

 is yet unknown to us, but which do pass 

 from one heavenly body to another. The 

 best established example of this yet ob- 

 tained is afforded in the case of the sun and 

 the earth. 



The fact that the frequency of magnetic 

 storms goes through a period of about 

 eleven years, and is proportional to the 

 frequency of sun spots, has been well 

 established. The recent work of Pro- 

 fessor Bigelow shows the coincidence to 

 he of remarkable exactness, the curves 



of the two phenomena being practically 

 coincident so far as their general fea- 

 tures are concerned. The conclusion is 

 that spots on the sun and magnetic 

 storms are due to the same cause. This 

 cause can not be any change in the ordin- 

 ary radiation of the sun, because the best 

 records of temperature show that, to what- 

 ever variations the sun's radiation may 

 be subjected, they do not change in the 

 period of the sunspots. To appreciate the 

 relation, we must recall that the researches 

 of Hale with the spectroheliograph show 

 that spots are not the primary phenomenon 

 of solar activity, but are simply the out- 

 come of processes going on constantly in 

 the sun which result in spots only in special 

 regions and on special occasions. It does 

 not, therefore, necessarily follow that a 

 spot does cause a magnetic storm. "What 

 we should conclude is that the solar activity 

 which produces a spot also produces the 

 magnetic storm. 



When we inquire into the possible nature 

 of these relations between solar activity and 

 terrestrial magnetism, we find ourselves so 

 completely in the dark that the question of 

 what is really proved by the coincidence 

 may arise. Perhaps the most obvious ex- 

 planation of fluctuations in the earth's 

 magnetic field to be inquired into would 

 be based on the hypothesis that the space 

 through which the earth is moving is in 

 itself a varying magnetic field of vast ex- 

 tent. This explanation is tested by in- 

 quiring whether the fluctuations in question 

 can be explained by supposing a disturb- 

 ing force which acts substantially in the 

 same direction all over the globe. But a 

 very obvious test shows that this explana- 

 tion is untenable. Were it the correct one, 

 the intensity of the force in some regions 

 of the earth would be diminished and in 

 regions where the needle pointed in the 

 opposite direction would be increased in 

 exactly the same degree. But there is no 



