be amused at the busy scene presented when a train is about to start. Here are the clerks taking money and dispersing tickets to first or second-class passengers going to various stations on the line; numerous porters wheel along the heaps of passengers' luggage; the superintendent is busy everywhere giving his directions; the guard is handing the passengers to their seats, and as the moment of starting approaches examines his timepiece, hung at his side in a leathern wallet; the engineer and his assistants, grim with coke-dust, are feeding with fuel and water their mighty steed, from whose huge form issue strange noises-the bubble-bubble of the heating water, the deafening hiss and scream of the hot vapor that struggles to burst its prison, and scatter death and destruction around, if not allowed an occasional outburst; while ever and anon a gigantic snort, and a few quick, impatient strokes of the piston, give startling warning. The first bell rings; the breathless loiterer who rushes into the station at the very last moment, and sorely tries the patience of the attendants with most unseasonable heaps of luggage, is pushed into a seat, feverish to the last with anxiety for the safety of his goods and chattels; the door is slammed after him, the guard mounts to his seat, the engineer makes some magical movement of his

hand, and the long train, with engine, carriages, passengers, and luggage, glides smoothly on, out of the stationhouse, past confused crowds of more trucks, carriages, and engines; past long and lofty piles of warehouses and engine-rooms, which appear, and glimmer, and vanish, before the dazzled eyes of the travellers; and the mighty mass, gathering speed as it goes, is soon bounding along over the open country.

Let us examine a little into the means by which this is accomplished; and, without attempting a scientific description of the several parts of a locomotive engine, endeavor to understand the general principles on which they are commonly constructed.

The sketch before us does not, nor could it, in so confined a space, exhibit every part of the beautiful machinery; but sufficient is shown to enable us, if not to see how every thing is done, to obtain a tolerable idea how it may be done.

I conclude that my readers are aware that water, when heated to the boiling-point, (which, at about the level of the sea, is at two hundred and twelve degrees of Fahrenheit's thermometer,) evaporates in steam. At this heat, steam, under the ordinary pressure, requires about 1700 times the space that was occupied by the water which pro