Such is a description, as given by the inventor, and it is singular to observe so much ingenuity and mechanical skill displayed in trying to perfect so complicated and extravagant a machine.

TINDALL AND BOTTOMLY'S PLAN.

The next account of an invention for reducing the expense of carriage on railways and other roads, emanated from Messrs. William Tindall and John Bottomly of Scarborough, in the form of a communication to the Society of Arts, dated June 4. 1814. They proposed that a rotatory motion should be given to wheels of carriages fixed to the axles by means of an endless chain passing over toothed wheels and grooved pulleys fixed on some convenient part of the axle of the wheels, and under and nearly round a toothed pulley turned by the power of the engine, which carriages were to be kept at proper or suitable distances by means of bars of iron, which served as joints. The chain was composed of circular and oval links placed alternately; the pulleys were toothed to suit the circular links, the indentations by which the teeth are produced being nearly

semicircular.

Intermediate pulleys were to be used, chiefly to press down the chains on the larger portions of the circumference of the other pulleys, or the axles of the wheels, which might, without inconvenience, be made of various sizes. The slack chain was hung over pulleys fastened to the arbor of the intermediate pulleys, but loose pulleys sufficed. They proposed a break to be used for descending planes.

SLOW PROGRESS OF INVENTION.

The absurdity of such propositions may now appear extraordinary; but those who know the difficulties which so often practically exist in making experiments, and the great outlay these involve, will be inclined to make every allowance for practical men, and it should induce those having the power and means to aid in trying, and not discouraging ingenious suggestions. By doing so, many years, perhaps, in the progress of useful improvements might be gained. The inventive genius of mankind does not appear to have advanced by hasty strides. Knowledge seems not to have been attained in the progress

of years, but rather that of centuries. The refinements of science and the achievements of art seem to have been gained like the slow gatherings of the gleaner. Successful invention, however, in some instances may be compared to a ray of light bursting on the tunnel's darkness; - how beautiful and distinct is the object when revealed! When the mystery is gone and the enigma is solved, how many then can lay hold of and successfully follow out the suggestion, heedless of those who, with blighted hopes, have laboured at it in vain !

BLACKET'S EXPERIMENTS.

About the year 1814 it became known that the progressive motion of the carriage neither required racks nor chains, to which, it appears, the failure of Trevithick's engine had been imputed. This fact, so essential in the science of locomotion, was proved by experiment on the Wylam railroad, for which Mr. Blacket of Wylam had an engine made in 1813, on Mr. Trevithick's plan, working on a plate rail, the friction of which would aid the experiment. He found that the adhesion on it was sufficient in ordinary gra

dients to make the wheels move onwards dragging a load of considerable weight. Mr. Blacket afterwards improved his engines and ascertained the quantity of adhesion. It is surprising how it should have been so long before this was ascertained. It is probable the error originated in the want of sufficient weight in the carriages experimented with; for of course it is now known that the adhesion or bite of the wheel is regulated by the pressure, and in proportion to the weight resting on the smooth surface, and to the extent of the surfaces in contact, or, in general terms, it may be said, that the bite of the wheel on the iron rail depends much on the weight of the carriage,

STEPHENSON'S KILLINGWORTH LOCOMOTIVE.

The next locomotive engine was constructed about this period by Mr. George Stephenson, at Killingworth colliery, and was tried on the railroad there in 1814. It was considered a great improvement on the previous one. It was found to drag eight loaded carriages, about 30 tons, at the rate of four miles an hour. It had two vertical cylinders, each of 8 inches diameter,. and two feet stroke placed at each end of and

within a cylindrical boiler, having a tube of 20 inches passing through it. Two pair of wheels were worked with cranks placed at right angles, which were retained in their position by means of an endless chain passing round two cogged wheels.

C

B

K

B

Fig. 49.

Fig. 49. shows the mode by which motion was communicated to the carriage wheels; A A, are the wheels; B B, the carriage frame; a, b, c, d, connecting rods, giving the motion from the piston to the cranks, which turn the two cog-wheels, e, f; these again turn the two larger cog-wheels KK fixed in the axles, and move the carriage wheels.

This plan of connecting the wheels was soon found inconvenient; and to obviate the defects, Mr. G. Stephenson and a Mr. J. Dodd took out a patent in 1815 for a method of communicating the power to the engine without those cog-wheels. One plan proposed was the application of a pin