This section is from the "A Plain Guide To Investment And Finance" book, by Lawrence R. Dicksee. Also see Amazon: A Plain Guide To Investment And Finance.
1. The earth is traversed by magnetic currents - directly dependent upon the heat derived from the sun - which produce the pointing of the compass-needle to the north pole (or rather at present to the west of north). At regular intervals the needle, in whatever part of the earth it be placed, undergoes violent and erratic oscillations - departing vehemently from its diurnal excursions both in range and intensity. This is the result of a disturbed condition of the earth's normal magnetic state, and the effects are termed a magnetic storm. These storms coincide exactly in the recurrent periods of their occurrence with the times when the spots (as marking the existence of portentous solar convulsions) attain their maximum amount - the swings of the needle (as signs of the storm) being more frequent and more intense when the spots are copious, and less violent when the spots are few. The doctrine which has long been accepted is the recognition of a direct causal connection between these storms and extensive areas of spots. At such periods the currents of electricity traversing the earth's surface become so strong that communication by means of telegraph wires is rendered impracticable.
1 Or expressed in another form: if the sun's distribution of heat and light be divided into about 22 hundred million of parts the earth obtains one part only.
2. The displays of the Aurora Borealis (a phenomenon caused by electric discharges in rare air) invariably become more frequent, resplendent and general (appearing in both hemispheres) when the spots are numerous and large. As a matter of fact the magnetic storm accompanies the wider auroral manifestations. It has been shown that an almost perfect parallelism exists between the curves of auroral frequency, brilliancy and range, and those of spot abundance: the highest intensity of auroral phenomena exactly corresponding with the larger development of spots, and the period of sparseness or absence of spots synchronising precisely with the diminution in area and vividness of auroral appearances. It is an accepted doctrine that a direct connection exists between the condition of the sun (as indicated by the varying proportion of his spots) and this celestial phenomenon. It may be added that the influence of solar disturbances is propagated with the velocity of light.
3. It is needless to point out how vitally the material condition of the earth - its storms and consequent shipwrecks and marine insurance losses; its agricultural fertility or barrenness; its droughts and consequent famines, and the luxuriance or failure of its crops, are causally associated with the state of its atmosphere, surface, and underground, as affected by these magnetic and electrical tempests. But I proceed to present a summary of specific statistics which have been collected.
4. Dr. Meldrum, of the Observatory at Mauritius, has shown from an examination of records (comprising two different spot periods) that the number, duration and violence of cyclones in the Indian Ocean have been greatest at a spot maximum - that is, when the energy of the sun was most pronounced - decreasing to a minimum in length and fierceness at the point when the solar maculation was least. Comparing the number of cyclones at two successive maxima of spots with those at two successive spot minima, I find that the ratio is nearly that of two to one. Indeed, Sir Norman Lockyer has expressed the view - perhaps too broadly - that the entire question of cyclones is simply a question of solar activity. This connection we can understand: at a period of extensive spots the sun's energy is at its maximum, and the communication of that augmented activity to our atmosphere accounts for the causation of winds of exceptional severity.
5. It would naturally follow that the number of shipwrecks and consequent marine insurance claims would vary directly with the frequency of destructive storms, and Mr. H. Jeula, from an examination of the records of losses at Lloyd's, and adopting two complete cycles of eleven years each, has ascertained that, during four years of each cycle when fewest spots appeared, the average percentage of loss in respect of registered vessels of the United Kingdom and the Channel Islands was 11.13, while during the three years of the greatest spot frequency the percentage was 1249, or an excess of more than 12 per cent, beyond the smaller figure.
6. Dr. Hunter, Director-General to the Government of India, has shown the periodicity of famines in Southern India caused by the failure of the rice crops as the consequence of deficient rainfall or drought, and that famines coincide with the minimum period of spots - the term of the recurrence of famines being nearly eleven years, or showing the same interval of time as that of sun spot freedom. Here again we may conceive that since the comparative absence of spots implies the more unbroken expanse of the photosphere, a larger supply of heat is radiated, with a consequently increased evaporation of water from rivers and streams in the form of aqueous vapour. It has been shown by Dr. Meldrum that the rainfall was greater at times of maxima of sun spots.
7. Bearing again upon the question of rainfall (or the absence of drought), it has been shown, as stated, that rainfall and atmospheric pressure in India vary in a periodic manner corresponding to the ten to eleven yean between a solar maximum and maximum of spots - that is, in years of maximum spots the summer rainfall is above, and the winter rainfall below the average, while in the years of minimum spots the cases are reversed. From records kept at Oxford it was ascertained that a greater abundance of rain fell when the spots were most numerous and extensive.
8. The question of the causation of any effect upon the earth's temperature (one of the factors of its productiveness) has been to an extent investigated. The most trustworthy mode of inquiry, remarked Mr. R. A. Proctor, is the examination of underground temperature, and here it has been discovered, through the researches of Professor Piazzi Smyth, at Edinburgh, that a slight increase of temperature occurs at the time when spots are least numerous.
 
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