Edward Sabine to Faraday   11 September 1850

Geneva, Sept. 11h, 1850.

Dear Faraday,

Capt. Younghusband¹ has informed me of the communications which you have lately had with him; I rejoice greatly that any of your investigations should lead you to desire a knowledge of the facts which we have been engaged in obtaining, or give you a prospect of being able to throw light on their causes. I need not add how delighted w<<e>> shall be able to arrange the facts in such ways as shall be either most clear to your apprehension, or illustrative of your opinions. Younghusband tells me you are pleased with the plate in the Hobarton Volume, shewing the diurnal movements of the magnetic direction & force in each month of the year in that quarter of the Globe². I have a precisely similar drawing (not yet lithographed) of the diurnal variation in direction & force in the different months at Toronto, as nearly as maybe in the same Latd as Hobarton, but in the other hemisphere. It is in a drawer in my cottage, and I will have it copied for you, if you wish it, immediately I return, which will be early next month. It will be lithographed in the 2d Vol. of the Toronto Obs, of which the printing is now commencing³; but you can make any use of it, or indeed of any thing else of mine, that may suit you. I am now engaged on a plate, for which I have the materials with me, which will exhibit the actual curve made by the one extremity of a freely suspended needle in its mean diurnal motion in every month of the year at the 4 observatories of Toronto, Hobarton, St. Helena, & the Cape of Good Hope⁴. I mention this because I think it is exactly the plate that will suit you, and I will endeavour to have it ready for you towards the end of October, if you wish it. It will differ from plates such as the one you have seen for Hobarton, inasmuch as it will shew the actual movement which the end of the needle would itself describe on a [two words illegible] perpendicular to the axis of the needle. The plate you have seen exhibits the movements in Declination & Inclination. If the 2 kinds of plate belonged to a station on the magnetic Equator, they would be identical; but every where else they differ; the movement in declination requiring to be multiplied by the cosine of the Inclination when the representation is to be of the space travelled over by the needle.

We are on our way home via Paris, but if you have occasion to write, send your letter to Capt. Younghusband who will forward it.

always truly yours | Edward Sabine

Address: M: Faraday Esq. | Royal Institution | Albemarle St.