Tony,
I found the letter tonight. Years ago I had printed it out from the microfilm and put it in a scrapbook. The letter is found on Reel 22 of the Western Reserve Historical Society Shaker Collection Microfilm, IV-A:46, FB. The genealogical connection to Mother Ann Lee of the Shakers is outlined by Arthur in the second to the last paragraph. To convey Arthur's style and emphasis, I have indicated in parentheses where he has underlined words or increased the size of the print to stress a point.
Here is the letter:
"Fair View," Netherton, Worc.,.
6th November 1902

A.G,. Hollister, Esq.
My Dear Sir,
I thank you for the instructive pamphlets you have so kindly sent to me, which I have read with real interest and sympathy. On the sex-union question, I am entirely with you. I have held your view, and practiced it, ever since my marriage (or rather, my wedding) ten years ago. My mother, (since dead) being a confined invalid, a mistress of my house was necessary, and on that account chiefly I was induced, when 25 years old, to wed a Christian lady of equal age. We have lived together in almost perfect harmony since our wedding day--never forgetting that we are "not as the beasts that perish," bur remembering that we have each a spiritual["spiritual" underlined] nature which must rule the physical ["physical" underlined], and take precedence in all things.
I can accept your teaching generally ["generally" underlined]; but with regard to Spiritualism I have personally had no experience and can therefore only say "I don't know." Certainly I have heard it roundly condemned as a "devilish doctrine," but for my own part I present an open mind on the subject.
Until the commencement of the War in South Africa, I was a member of the church of Christian Brethren, but I felt morally bound to sever my connection with them owing to their attitude on the War. Being a preacher ["preacher" underlined] among them, I desired to condemn ["condemn" underlined] it, as inconsistent with the teaching of Christ, and as an outrage on the "Christian profession" of this country, but I was not allowed to do so. Therefore I came out ["came out" underlined] from them, and have remained separate ["separate" underlined] ever since. Twelve months ago I felt overwhelmingly impressed ["overwhelmingly impressed" underlined] to found the League of Peace and publish "The Banner of Peace," which, from a pecuniary point of view, has been a considerable out-of-pocket loss. Next year, however, I hope to recoup myself from the renewed subscriptions which will no doubt flow in.
I send you a copy of my book "A Strong Delusion" ["A Strong Delusion"underlined]--but in doing so I should warn you that it does not altogether reflect my present views ["present views" underlined],--though in my condemnation of Priestcraft ["Priestcraft" underlined] my attitude remains entirely unchanged. Please, therefore, remember this when you read therein anything which meets with your disapprobation. Remember also that I am comparatively a young man [36] who is seeking the Truth, and not one who claims to have already attained it. One by one I have thrown overboard many of the 'beliefs' in which I have been brought up.
And now in conclusion I will tell you something that will be sure to interest you. Your prophetess, Ann Lee, when she sailed for America on the 19th May, 1774, left behind her a brother (Joseph)[name "Joseph" underlined], who had never identified himself with his sister's teaching and claims, and therefore perhaps has never been mentioned in your publications. This brother was my direct ancestor. [This last sentence is in large print and underlined]. During the past century the Lee family has progressed in a worldly sense, so that now some of us are well-to-do and hold positions of honour and influence in the Civil Service of the Government, and others in the Established Church.
In the hope, my dear Sir, that myself and the Shaker Community may become better acquainted in the not distant future,
Believe me,
Yours very faithfully,
Arthur Lee
(writing under the nom-de-plume of "Arnold de Lisle.")

[Note: This last phrase in parenthesis about the non-de-plume is written by Arthur in the text and is not a comment in parentheses added by me].

So, Tony, there it is. As I have re-read the letter, I realize that my memory was faulty on two points. First, I said that he had signed his letter to Brother Alonzo as "Arnold D'Lisle," but it turns out that he signed it "Arnold de Lisle"--small "d," no apostrophe. Secondly and more importantly, I had said that Arthur had said that he was descended from a brother of Ann's named John, but upon re-reading the letter I find that he says he is descended from a brother of hers named Joseph--Joseph Lee.
I'm very much looking forward to hearing your thoughts on all of this and I have more material to send to you.