“The use of the chronometer is to ascertain the longitude,” said Harry, “and the manner of doing it is, simply this:  A chronometer is nothing more nor less than a watch, made with more care than usual, so as to keep the most accurate time.  They are of all sizes, from that of a clock, down to this which I wear in my fob, and which is a watch in size and appearance.  Now, the nautical almanacs are all calculated to some particular meridian—­”

“Yes,” interrupted the relict, “Mr. Budd had a great deal to say about meridians.”

“That of London, or Greenwich, being the meridian used by those who use the English Almanacs, and those of Paris or St. Petersburg, by the French and Russians.  Each of these places has an observatory, and chronometers that are kept carefully regulated, the year round.  Every chronometer is set by the regulator of the particular observatory or place to which the almanac used is calculated.”

“How wonderfully like my poor, dear Mr. Budd, all this is, Rosy!  Meridians, and calculated, and almanacs!  I could almost think I heard your uncle entertaining me with one of his nautical discussions, I declare!”

“Now the sun rises earlier in places east, than in places west of us.”

“It rises earlier in the summer, but later in the winter, everywhere, Mr. Mulford.”

“Yes, my dear Madam; but the sun rises earlier every day, in London, than it does in New York.”

“That is impossible,” said the widow, dogmatically—­“Why should not the sun rise at the same time in England and America?”

“Because England is east of America, aunty.  The sun does not move, you know, but only appears to us to move, because the earth turns round from west to east, which causes those who are farthest east to see it first.  That is what Mr. Mulford means.”

“Rose has explained it perfectly well,” continued the mate.  “Now the earth is divided into 360 degrees, and the day is divided into 24 hours.  If 360 be divided by 24, the quotient will be 15.  If follows that, for each fifteen degrees of longitude, there is a difference of just one hour in the rising of the sun, all over the earth, where it rises at all.  New York is near five times 15 degrees west of Greenwich, and the sun consequently rises five hours later at New York than at London.”

“There must be a mistake in this, Rosy,” said the relict, in a tone of desperate resignation, in which the desire to break out in dissent, was struggling oddly enough with an assumed dignity of deportment.  “I’ve always heard that the people of London are some of the latest in the world.  Then, I’ve been in London, and know that the sun rises in New York, in December, a good deal earlier than it does in London, by the clock—­yes, by the clock.”

“True enough, by the clock, Mrs. Budd, for London is more than ten degrees north of New York, and the farther north you go, the later the sun rises in winter, and the earlier in summer.”