We will now resume our history of the early locomotives in America, believing that our readers will pardon our digression.

As it may be interesting to railroad engineers and machinists, we insert here the conditions required and the premium offered by the Baltimore and Ohio Railroad company for the best locomotive of American manufacture, which were Referred to in Mr. Latrobe's letter to the author: true, adapted to their road, the president and directors hereby give public notice that they will pay the sum of four thousand dollars for the most approved engine which shall be delivered for trial upon the road, on or before the 1st of month, 1831; and they will also pay three thousand five hundred dollars for the engine which shall be adjudged the next best, and be delivered as aforesaid, subject to the following conditions, to wit:

"The engine must burn coke or coal, and must consume its own smoke.

"The engine, when in operation, must not exceed three and one-half tons' weight, and must, on a level road, be capable of drawing, day by day, fifteen tons, inclusive of the weight of the wagons, fifteen miles per hour. The company to furnish wagons of Winans's construction, the friction of which will not exceed five pounds to the ton.

"In deciding on the relative advantages of the several engines, the company will take into consideration their respective weights, power, and durability, and, all other things being equal will adjudge a preference to the engine weighing the least.

"Fourth. The flanges are to run on the inside of the rails. The form of the cone and flanges, and the tread of the wheels, must be such as are now in use on the road. If the working parts are so connected as to work with the adhesion of all the four wheels, then all the wheels shall be of equal diameter, not to exceed three feet; but if the connection be such as to work with the adhesion of two wheels only, then those two wheels may have a diameter not exceeding four feet, and the other two wheels shall be and a half feet in diameter, and shall work with Winans's friction-wheels, which last will be furnished upon application to the company. The flanges to be four feet seven and a half inches apart, from outside to outside. The wheels to be coupled four feet from center to center, in order to suit curves of short radius.

"The pressure of steam not to exceed one hundred pounds to the square inch, and, as a less pressure will be preferred, the company, in deciding on the advantages of the several engines, will take consideration their relative degrees of pressure. The company will be at liberty to put the boiler, fire-tube, cylinder, etc., to the test of a pressure of water not exceeding three times the pressure of the steam intended to be worked, without being answerable for any damage the machine may receive in consequence of such test.

"There must be two safety-valves, one of which must be completely out of the reach of the engine-man, and neither of which must be fastened down while the engine is working.

"The engine and boiler must be supported on springs and rest on four wheels, and the height from the ground to the top of the chimney must not exceed twelve feet.

"There must be a mercurial gauge affixed to the machine, with an index-rod, showing the steam-pressure above fifty pounds per square inch, and constructed to blow out at one hundred and twenty pounds.

"The engines which may appear to offer the greatest advantages will be subjected to the performance of thirty days' regular work on the road; at the end of which time, if they shall have proved durable, and continue to be capable of performing agreeably to their first exhibition, as aforesaid, they will be received and paid for as here stipulated.

"N. B.—The railroad company will provide and will furnish a tender and a supply of water and fuel for trial. Persons desirous of examining the road, or of obtaining more minute information, are invited to address themselves to the president of the company. The least radius of curvature of the road is four hundred feet. Competitors who arrive with their engines before the 1st of June, will be allowed to make experiments on the road previous to that day.

"The editors of the National Gazette, Philadelphia, Commercial Advertiser, New York, and Pittsburgh Statesman, will copy the above once a week, for four weeks, and forward their bills to the Baltimore and Ohio Railroad Company."

As Mr. Latrobe says in his letter before quoted, Phineas Davis's engine, built at York, Pennsylvania, was the only one which came up to the requirements of the company. After a trial, and several modifications and changes, each as it suggested itself, late in the summer of 1831, the Davis (or rather "Davis and (partners") engine was found capable of pulling on the part of the road between Baltimore and Ellicott's Mills, thirteen miles, four loaded cars of the gross weight of fourteen tons, in satisfactory time.

This engine was mounted on wheels like those of the ordinary cars, thirty inches in diameter, and its velocity was effected by means of gearing with a spur-wheel and pinion on one of the axles of the roads wheels.

In the construction of the road from Baltimore to the Point of Rocks, every mode hitherto suggested by science or experience had been tested, and thus the work must be regarded as having the honor of solving most of the problems which presented themselves in this early period of railroads in this country. The granite, and the iron rail; the wood and iron, on stone blocks; the wood and iron on wooden sleepers, supported by broken stone; the same supported by longitudinal ground-sills in place of broken stones; the log-rail, formed of trunks of trees, worked to a surface on one side to receive the iron, and supported by wooden sleepers; and the wrought-iron rails of the English mode—had all been laid down, and as early as 1832 formed different portions of the work. Great credit is therefore due to the engineers and workmen of this road, for the patience displayed in carrying out their work, at that time the longest in the world; nothing in England could approach it in the magnitude and extent of its plan. These men labored long, at great cost, and with a diligence which is worthy of all praise. Their road and workshops have been a lecture-room to thousands who are now practicing and improving upon their hard-earned experience.