Can you give some background on the Ark Edition of “Science and Health”?

The edition of Science and Health with the illustration of an ark imprinted on the front cover, commonly known as the “Ark Edition,” is the second edition of Science and Health. It was published in 1878. The last three chapters of this edition were new.
Eddy originally intended this second edition to be “a book over five hundred pages” that would give “a fuller synopsis of our metaphysical system” (Science and Health, 2nd edition, 5). The printer’s proofs were so filled with typographical errors that Eddy could only salvage 167 pages and so had to publish a shorter version of her textbook. She labeled it “Vol. II” on the spine and title page because she wanted the public to consider it in conjunction with the first edition of Science and Health, published three years earlier in 1875.