Faraday to Edward Sabine   17 September 1850

Royal Institution | 17 Septr. 1850

My dear Sabine

I am afraid you will think I am dreaming or else I am sapping the very foundations of terrestrial magnetism as it at present stands but indeed I cannot help it mine are experimental researches and the foundation is a foundation of facts[.] Very likely I may have erred in the conclusions I have raised upon it but the facts cannot alter. I received yours yesterday¹ and thank you for its kindness which I was sure of[.] I intended to have written to you before but have been so occupied. The paper which I have now finished and which is in the hands of the copyist that it may go in quickly to the R.S. and take date is above 100 pages² & is preceded by one already sent in of more than 40³ and there is as much more matter waiting till I get my aching head a little rested. I thought it not only a pleasure but a duty to tell you, who have distinguished yourself so much in this branch of Science, first of their facts and except some general remarks which would fall out in communication with Whewell, Captn. Younghusband⁴ & some others I have reserved myself for you. I think you had better say nothing about the matter until you come home that the thing may be fairly dated & known at the Royal Society and here first. When the matter is published either by reading or printing it is the property of all but before that I like to have possession of my own game.

Now for a few facts. Oxygen is highly magnetic nitrogen not at all. If one takes a given weight of oxygen and then take seventeen times its weight of crystallised proto sulphate of iron which is a good magnetic salt and dissolve that in as much water as will equal the bulk of the oxygen the solution & the gas then have equal magnetic power. Oxygen is at ordinary temperatures in the state of iron when by heat it is just upon losing its magnetic force the addition of heat rapidly diminishes the magnetic power of oxygen the lowering of its temperature rapidly increases it. Besides that rarefying oxygen alters its magnetic force at half an atmosphere it has, as far as I can tell yet, it has half the power[.] All these qualities it carries into the atmosphere unchanged except that they are diluted to a certain extent by the nitrogen but all that happens to oxygen happens to air[.]

The Sun in his daily course heat[s] & expands the oxygen of the air with the air and is continually changing its magnetic condition hence affections of the lines of force from the earth and as I believe of all the diurnal and annual variations and of many other natural magnetic effects which I have classed together in my paper under the title of Atmospheric magnetism. The results of induction beautifully accord with Observations but I want to know more of the dip than I can get as yet.

Many conclusions flow from these principles which are new & have not occurred to the minds of philosophers. There is one very serious one and when I think of it I am almost sorry for it but I hope it may not be so important as my fears represent it. The magnetic force of the Earth is not shewn by the needle: Being in a magnetic medium which can change and does change continually the needle when employed to measure force measure the joint result of the two actions which sometimes coincide and sometimes oppose each other and of which the needle gives no indication. When by temperature the conducting power of the air or oxygen for the magnetic force is changed the needle shews such change at a higher temperature indicating increased action & at a lower temperature diminished action and yet there has been no change in the amount of power during the whole time either at the Source in the Earth or in the neighbouring space - and many other shapes does this two fold action on the needle take. This for the present you will soon be at home & I shall be anxious to tell you all, even far more than is written[.] I am in hopes that you can get at the paper at the RS as our Secretary⁵ & judge it and so help me to a quick publication for I do not think I could wait as I did for the publication of the last paper⁶[.]

Many many thanks for your kind offers[.] There will be time enough to consider the matter when you come home. Captn Younghusband has been very kind too and has let me have the MS. data which when you come I shall perhaps ask you about as appendix to my paper⁷.

St Helena as you may imagine is a very fine case & I am gradually unravelling it but the statement of principles &c made the last paper so long that I have kept it with the Cape of Good hope the night action & other points for the next paper⁸[.]

With kindest remembrances to Mrs Sabine⁹ I am my dear friend

Most Truly Yours | M. Faraday

Coll Sabine RE | &c &c &c