An excellent article on Joseph Smith's role as 'translator' appeared in Meridian Magazine on November 18, 2013:
...The obvious evidence of Joseph’s gift to translate is the Book of Mormon (originally engraved on metal plates in reformed Egyptian hieroglyphs). The year Moroni delivered these plates to Joseph, ancient Egyptian was a dead language to the world. The Rosetta Stone had only recently been discovered in Egypt, but it took French scholars seven years to decode the Egyptian hieroglyphs on it.  While they were working to translate one page from Egyptian, the Prophet Joseph translated and produced an entire book over 500 pages long. They took over twenty years to confidently translate one page, but Joseph zipped through his translation in only two months. Elder Maxwell commented on this marvelous work and wonder, pointing out that Joseph translated the Book of Mormon faster than most of us read it:
“One marvel is the very rapidity with which Joseph was translating--at an estimated average rate of seven to ten of our printed pages per day!  The total working time was about 65-75 working days. 
“One able LDS translator in Japan, while surrounded by reference books, language dictionaries, and with translator colleagues available, if needed, recently indicated that he considers an output of one careful, final page a day to be productive. And he is re-translating from earlier Japanese to modern Japanese!
“Over 50 able English scholars labored for seven years, using previous translations, to produce the precious King James Bible, thus averaging about one precious page per day!” 
“Second, from what we know, rarely would Joseph go back, review, or revise what he had already translated…The Prophet’s dictating flowed, resulting just as the compositor, John H. Gilbert, remembered with no paragraphing....The process not only flowed, but it flowed at a very rapid rate under the gift and power of God.
If one were manufacturing, he would constantly need to cross-check himself, to edit, and to revise for consistency. Had the Prophet thus dictated and revised extensively, there would have been more evidence of it. Thus whatever the details of process, we are discussing an astonishing process!
“Furthermore, Emma Smith said of the inspired process, ‘After meals, or after interruptions, [Joseph] would at once begin where he had left off, without either seeing the manuscript or having any portion of it read to him.’  Usually, one who has been dictating and has been interrupted, must resume by inquiring ‘Now, where were we?’ Not so with the Prophet!” 
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