another forum wrote: It is indeed in History of the Church, vol. 6, ch. 19, under the heading "Address of the Prophet—His Testimony Against the Dissenters at Nauvoo." (I love BYU's access to GospeLink . . .)
Here's how to get there: go to lib.BYU.edu and select "Religion - LDS" from the "Find Databases by Subject" drop-down menu. Click "Go." GospeLink.com will come up at the top of the list. Click on it and enter your Route Y ID and password when prompted. You can then search the entire collection of GospeLink, or browse anything you wish.
Unfortunately, I have no access ...