Others of his fellow-passengers gave testimony to the same effect, and Captain Pell stated under oath that, when he saw the completed instrument in 1837, he recognized it as embodying the principles which Morse had explained to him on the Sully; and he added: "Before the vessel was in port, Mr. Morse addressed me in these words: 'Well, Captain, should you hear of the telegraph one of these days as the wonder of the world, remember the discovery was made on board the good ship Sully.'" Morse always clung tenaciously to the date of 1832 as that of his invention, and, I claim, with perfect justice. While it required much thought and elaboration to bring it to perfection; while he used the published discoveries of others in order to make it operate over long distances; while others labored with him in order to produce a practical working apparatus, and to force its recognition on a skeptical world, the basic idea on which everything else depended was his; it was original with him, and he pursued it to a successful issue, himself making certain new and essential discoveries and inventions. While, as I have said, he made use of the discoveries of others, these men in turn were dependent on the earlier investigations of scientists who preceded them, and so the chain lengthens out. There will always be a difference of opinion as to the comparative value of a new discovery and a new invention, and the difference between these terms should be clearly apprehended. While they are to a certain extent interchangeable, the word "discovery" in science is usually applied to the first enunciation of some property of nature till then unrecognized; "invention," on the other hand, is the application of this property to the uses of mankind. Sometimes discovery and invention are combined in the same individual, but often the discoverer is satisfied with the fame arising from having called attention to something new, and leaves to others the practical application of his discovery. Scientists will always claim that a new discovery, which marks an advance in knowledge in their chosen field, is of paramount importance; while the world at large is more grateful to the man who, by combining the discoveries of others and adding the culminating link, confers a tangible blessing upon humanity.