460 F. H. Bigelow — Solar and Terrestrial Magnetism. 



magnetic field. Thus we have undoubted evidence that the 

 entire magnetic and meteorological systems go through 11-year 

 fluctuations, synchronous with the sun spots which register 

 the solar conditions. These are indicated on pages 121-125, 

 where the data is greatly abbreviated irom the compilations in 

 our hands. It may be said in passing that the brief abstract 

 before us does but scant justice to the material of the research. 

 This, however, it was very difficult to publish in its entirety, and 

 scientists must feel at a real disadvantage in estimating the 

 soundness of some of our conclusions, unless they go through 

 the great labor of reproducing similar data for themselves. 

 We might give much more evidence from several other sources 

 in favor of the long period variations, but this subject is already 

 well known, and our only contention here is that the electric 

 current theory of the upper atmosphere looks like transposing 

 an effect into an efficient cause, unless it is proposed to make 

 the earth wag the sun to fill out the explanations. 



I have made the position prominent in the Bulletin that the 

 earth is plunged in two external magnetic fields, because we 

 have two distinct vector systems which demand that interpreta- 

 tion. The first was concerned with the long and short aperiodic 

 terms, the Eschenhagen very quick variations, the disturbances, 

 and the long range fluctuations, as well as the period correspond- 

 ing with the rotation of the sun on its axis. The second is 

 wholly confined to the diurnal variations of the needle and the 

 annual period within these elements. This second field is 

 illustrated on pages 85-92, and it is characterized by the phe- 

 nomenon of magnetic refraction at the surface of the earth, and 

 by the existence of sets of couples, which also forces us to the 

 conclusion that the earth has a permeable shell, and that the 

 field itself is associated with the polar radiations of light. This 

 vector system changes with the year northward and southward, 

 and always follows the declination of the sun, but the material 

 for showing that is entirely omitted from the Bulletin. At any 

 rate the two vector systems each indicate that the outer shell 

 of the earth is more permeable to these external fields than the 

 entire body of the earth itself. 



We have at this point broken with current opinion, and that 

 too, curiously, in two opposite directions. It is objected that 

 the electromagnetic field cannot act as a steady field because it 

 is too rapid. We reply that it is so rapid that our exploring 

 magnets by their inertia cannot pick up the changes, and that 

 they register as if the field were steady. On the other hand it 

 is objected that the common polar magnetic field is too quiet, 

 has no currents of electricity, and therefore no power to pro- 

 duce changes of temperature by transmitting energy. But we 

 quote some propositions from Heaviside's papers to show that 



