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The Reverend Henry Caswall
Publisher of an anti-Mormon book The City of the Mormons; or, Three Days at Nauvoo in 1842.
On 19 April 1842, an English clergyman from Missouri named Henry Caswall visited Nauvoo. Caswall subsequently published an anti-Mormon book called The City of the Mormons; or, Three Days at Nauvoo in 1842. Caswall introduces his book as follows:
The following narrative, the result of a few weeks' leisure on shipboard, is presented to the Christian public, with a deep sense, on the Author's part, of the iniquity of an imposture, which, under the name of religion, is spreading extensively in America and in Great Britain. Mormonism needs but to be seen in its true light to be hated; and if the following pages, consisting almost exclusively of the personal testimony of the Author, should assist in awakening public indignation against a cruel delusion and a preposterous heresy, he will consider himself amply rewarded. A History of Mormonism, from its commencement to the present time, may perhaps form the subject of a future publication. Liverpool, June 19, 1842
The book in its entirety may be viewed on Google Books: "The City of the Mormons; or, Three Days at Nauvoo in 1842."
Caswall's story of Joseph Smith "translating" a Greek psalter
During his visit to Nauvoo, Caswall would later claim that he had shown Joseph Smith a Greek psalter, which the Prophet claimed to translate:
He [Joseph Smith] has a downcast look, and possesses none of that open and straightforward expression which generally characterizes an honest man. His language is uncouth and ungrammatical, indicating very confused notions respecting syntactical concords. When an ancient Greek manuscript of the Psalms was exhibited to him as a test of his scholarship, he boldly pronounced it to be a "Dictionary of Egyptian Hieroglyphics." Pointing to the capital letters at the commencement of each verse, he said, "Them figures is Egyptian hieroglyphics, and them which follows is the interpretation of the hieroglyphics, written in the reformed Egyptian language. Them characters is like the letters that was engraved on the golden plates." 
For a detailed response, see: Joseph Smith/Translator/Greek psalter
- Henry Caswall, The Prophet of the Nineteenth Century (London: J.F.G. & J. Rivington, St. Paul's Church Yard and Waterloo Place, Pall Mall, 1843), 223.