The difference of these recognitions may be illustrated by supposing certain travelling philosophical instruments, endowed with intelligence and the power of speech, to come together in their wanderings,--let us say in a restaurant of the Palais Royal. "Very hot," says the talking Fahrenheit (Thermometer) from Boston, and calls for an ice, which he plunges his bulb into and cools down. In comes an intelligent and socially disposed English Barometer. The two travellers greet each other, not exactly as old acquaintances, but each has heard very frequently about the other, and their relatives have been often associated. "We have a good deal in common," says the Barometer. "Of the same blood, as we may say; quicksilver is thicker than water." "Yes," says the little Fahrenheit, "and we are both of the same mercurial temperament." While their columns are dancing up and down with laughter at this somewhat tepid and low-pressure pleasantry, there come in a New York Réaumur and a Centigrade from Chicago. The Fahrenheit, which has got warmed up to _temperate_, rises to _summer heat_, and even a little above it. They enjoy each other's company mightily. To be sure, their scales differ, but have they not the same freezing and the same boiling point? To be sure, each thinks his own scale is the true standard, and at home they might get into a contest about the matter, but here in a strange land they do not think of disputing. Now, while they are talking about America and their own local atmosphere and temperature, there comes in a second Boston Fahrenheit. The two of the same name look at each other for a moment, and rush together so eagerly that their bulbs are endangered. How well they understand each other! Thirty-two degrees marks the freezing point. Two hundred and twelve marks the boiling point. They have the same scale, the same fixed points, the same record: no wonder they prefer each other's company!