It is necessary here to observe that the invention of the mariner’s compass, and of gunpowder and cannon, have been ascribed to the Chinese as well as the invention of wood engraving and block-printing; and it has been conjectured that _very probably_ Marco Polo communicated to his countrymen, and through them to the rest of Europe, a knowledge of those arts. Marco Polo, however, does not in the account which he wrote of his travels once allude to gunpowder, cannon, or to the art of printing as being known in China;[I-35] nor does he once mention the compass as being used on board of the Chinese vessel in which he sailed from the coast of China to the Persian Gulf. “Nothing is more common,” says a writer in the Quarterly Review, “than to find it repeated from book to book, that gunpowder and the mariner’s compass were first brought from China by Marco Polo, though there can be very little doubt that both were known in Europe some time before his return.”--“That Marco Polo,” says the same writer, “would have mentioned the mariner’s compass, if it had been in use in China, we think highly probable; and his silence respecting gunpowder may be considered as at least a negative proof that this also was unknown to the Chinese in the time of Kublai-Khan.”[I-36] In a manner widely different from this does Mr. Ottley reason, respecting the cause of Marco Polo not having mentioned printing as an art practised by the Chinese. He accounts for the traveller’s silence as follows: “Marco Polo, it may be said, did not notice this art [of engraving on wood and block-printing] in the account which he left us of the marvels he had witnessed in China. The answer to this objection is obvious: it was no marvel; it had no novelty to recommend it; it was practised, as we have seen, at Ravenna, in 1285, and had perhaps been practised a century earlier in Venice. His mention of it, therefore, was not called for, and he preferred instructing his countrymen in matters with which they were not hitherto acquainted.” This “obvious” answer, rather unfortunately, will equally apply to the question, “Why did not Marco Polo mention cannon as being used by the Chinese, who, as we are informed, had discovered such formidable engines of war long before the period of his visit?”