The work of Dr. Williams, of which I spoke, is a Second edition of that which thou hast seen, published in 1809, at Burlington Vt., in 2 8vo volumes, containing about 1000 pages. Much of it is written anew, & the additions are extensive & valuable. I know the Doctor would be highly gratified to have it read & applauded by thee. He prides himself on his Republican Sentiments, particularly in the 2d vol. of this edition.

Gen. S. Van Rensselaer, the proprietor of the Manor of Rensselaer Wyck,1 has a Chaise nearly finished, on my plan. The proportions as I propose. It will be in motion next week, when I shall close my Letter with an account of its success. Except to myself, the sight will be novel in Albany, & hundreds are curious & waiting to try it. I know that in overcoming a 6 inch obstacle, with a load of 500 pounds, at a standing draught, the wheel of 7 feet will effect an advantage, equal to 96 pounds, when compared with the wheel of 4 feet 8 inches: & I also know that on the crooked axle, the same power, that is, 250 pounds, carries the same load, with the same results, also at a standing draught. But, giving the impulse of motion, by permitting the wheels to roll a short distance before they meet the obstacle, there is also a gain in the cranked, over the straight axle, which is very considerable. I let the power fall over a pulley, in the above experiments. To carry the wheels of 4 feet 8 inches over the same obstacle, with the same load, I have to increase the power, (or weight over the pulley,) by the addition of 96 pounds to the power. The small wheels that I used, are a trifle short of 4 feet 8 inches diameter.

When the load & power are thus tried, first on the small, & then on the large wheels; first with straight & then with cranked axles; standing, & then in motion, when they meet the obstacle, I have a most complete series of experiments for demonstration: And such were the facts, on which my reasoning was founded.

When the wheels, loaded upon the straight axle, meet the obstacle, it is by a sudden stroke, which deadens the impulse; &, if they mount it, they do so by a joult as sudden;—when, on the contrary, the load is on the cranked axle, & the wheels meet the obstacle, the Shock is less violent, & the impulse acts with greater power, by a kind of eslastic effort: Nor is the joult near so great, in passing over.

The above experiments show that there is no loss of power, in employing the cranked axle, in order to reduce the height of the load, & the line of draught, raised too high by employing large wheels. And if this occasions no loss, it must effect a great gain;—by enabling me to employ large wheels, & by bringing the load nearer to the point of contact, the actual centre of motion: as well as by equalizing the draught, & the motion of the load. Every inequality of motion, increases the friction, & that in a greater degree than seems to have been considered.

Stages, which employ Jacks, (as they are called here by the Coach-Makers,) on which to fasten the leathers on which the body rests, have their loads from 2 to 3 feet above the centre of the wheels; & these of course are but low. The consequence of which is, a great disadvantage in the application of the power of the horses, and a loss of the power of at least one in five when passing over rough or uneven roads, by the increased friction occasioned by the position of the load. These Stages so frequently upset, that travelling in them excites general terror. At least 20 lives have been lost in this way, within the United States, during the last year. Were these vehicles constructed with wheels of 6 & 7 feet diameter, & their axles cranked to the ordinary or best line of draught for the horses, there would be little danger of upsetting, & I am confident the 4th or 5th horse might be spared from the team. A Stage proprietor here, proposes to make trial of my method. If my reasoning is correct, & my inferences fair, from numerous experiments, this subject well merits the attention of the Post-Master General. That Officer ought to, & probably would, consider the saving of lives deserving his2 attention; & he is the proper organ to foster such an improvement, as important to considerations of political economy. And if travelling in3 Stages were considered less tedious & tiresome, & more safe & free from danger, the travelling by them4 would increase, & the government would be enabled to make contracts for carrying the mails on better terms. I hope this subject may engage the attention of the intelligent Gentleman who conducts the concerns of the Post Office Department. Were he to encourage a fair trial on Some principal route, I am fully persuaded he would essentially contribute to the public interest. Between Washington & Baltimore, I found the roads excedingly bad; & there would be a good place to try improved Stages. Or, between this City & Schenectady;—if he would encourage the Contractors to try it, I would give the Right, & superintend the construction of a Carriage. The only objection to my construction, would be, that the Carriage would not turn on so little ground. Stages are made to go forward, & turning short, is but a little part of the object for which they are employed. A mason I once employed, objected to connecting the brick-work of my chimney back, in the fire place, by laying some of the bricks transversely, because of the difficulty of detaching the back end, when the back should need repairs: & when I persisted, proposed to use, for that purpose, Soft bricks!