Then there are steam sanding devices for locomotives by which sand is automatically fed to the rails at the same time the air brake is applied. Starting valves used for starting compound locomotives on ascending steep grades, in which both low and high pressure cylinders are supplied with live steam, and when the steam, exhausted from either high or low pressure cylinders into the receivers, has reached a predetermined pressure, the engine works on the compound principle. Single acting compound engines, in which two or more cylinders are arranged tandem, the steam acting only in one direction, and the exhaust steam of one acting upon the piston in the cylinder next of the series, are arranged in pairs, so that while one is acting downward the other is acting upward. Throttle valves automatically closed upon the bursting of a pipe, or the breaking of machinery, are operated by electricity, automatically, or by hand at a distance. Napoleon, upon his disastrous retreat from Moscow, anxious to reach Paris as soon as possible, left his army on the way, provided himself with a travelling and sleeping carriage, and with relays of fresh horses at different points managed, by extraordinary strenuous efforts day and night, to travel from Smorgoni to Paris, a distance of 1000 miles, between the 5th and 10th of December, 1812. This was at the average rate of about two hundred miles a day, or eight or nine miles an hour. It was a most remarkable ride for any age by horse conveyance. Within the span of a man’s life after that event any one could take a trip of that distance in twenty-four hours, with great ease and comfort, eating and sleeping on the car, and with convenient telegraph and telephone stations along the route by which to comunicate by pen, or word of mouth, with distant friends at either end of the journey. If Napoleon had deemed it best to have continued his journey across the Atlantic to America he would have been compelled to pass several weeks on an uncomfortable sailing vessel. Now, a floating palace would await him which would carry him across in less than six days. Should mankind be seized with a sudden desire to replace all the locomotives in the world by horse power it would be utterly impossible to do it. It was recently estimated that there were one hundred and fifty thousand locomotives in use on the railroads of the world; and as a fair average would give them five hundred horse power each, it will be seen that they are the equivalent of seventy-five million horses.