F. H. Bigelow — Solar and Terrestrial Magnetism. 461 



an unsteady polar field transmits energy accompanied by transient 

 currents of electricity, and that half this energy goes into 

 setting up the new state of the field and half into heat. 

 Furthermore the most probable explanation of magnetic lines 

 of force is that they are constructed of electric currents, in 

 rotation around the axis of the vortex tubes stretching from 

 the positive to the negative parts of the field. The whole 

 agency being dynamic, we can easily conceive that there is a 

 continuous effect upon the earth's atmosphere, either by direct 

 additions of energy, or by modifying terrestrial radiations, since 

 the solar field is perpetually in vibration. 



Evidently there is an immense mass of testimony to show 

 that something of the kind is going on continuously. For we 

 find that all the characteristics of the magnetic periods are 

 reproduced in the temperatures and pressures of the northwest ; 

 also in the location of the storm tracks from year to year, as 

 given in compressed form on pages 108-130. The three 

 elements, magnetic field, temperature and pressure, were all 

 handled in precisely the same way, at first tentatively seeking 

 to discover the law of inversion, which was forced upon our 

 attention by trying to carry the type curve through the changes 

 shown on the daily weather maps. As the outcome of much 

 work we are in this position : The temperature and the pressure 

 certainly must and do vary together, but the magnetic field on 

 the average gives us curves agreeing with either of these 

 elements, just as exactly as they do with each other ; our final 

 compilations being strictly mechanical along the lines of the 

 general law. It must be remarked that in comparing the 

 curves of the individual periods with each other there is much 

 looseness and irregularity, so that even a friendly investigator- 

 may superficially conclude that I have been tempted to force my 

 data to my conclusions, while an unsympathetic critic may find 

 himself willing to throw out the entire subject on the ground 

 of individual discrepancy. Neither would be right in such a 

 decision, for there is no possible ground of intimating more 

 than that I may have been mistaken in my judgments. 

 Still, to guard against this possible issue, the work has been 

 done over and over again in at least four combinations, in such 

 a way that it would be impossible to remember former assign- 

 ments of direct or inverse type. In all cases about 75 per 

 cent of the curves get the same interpretation, and this was 

 true for one of my assistants as well as for myself. There is 

 some need of practice and aptitude in dealing with such curves 

 as these, but perhaps nothing better can be done with the sub- 

 ject-matter itself at present. Even in such simple curves as 

 the diurnal variations of the magnetic forces, wild discrepan- 

 cies are encountered ; in the case of our nine-crested curve, 



