242 



"I send you the drawing of a coal \vagon. * *■ * I have taken 

 a great deal of paiiis with the drawing, and consider it a very good one. 

 I have investigated very thoroughly the force of traction, and also the 

 economy of using lai-ge wheek. A wagon like the drawing will be very 

 economical for the transpoitation of coal. * * * Yf^Q all know that 

 a good team on a good common earth road ought to draw one and a 

 half tons; this multiplied by 4 will give six tons, exclusive of wagon, 

 for a plank road. This result is given on the supposition that both 

 wagons are of the same size ; but in the drawing the wheels are 7 feet 

 in diameter, or nearly twice the size of a common wagon wheel. We 

 know a.s the size of wheels is increased, power is gained ; therefore, by 

 the use of wheels of 7 feet diameter, a span of horses ought to draw 

 nearly 12 tons, all of the wheels l)eing of the same size. This wagon 

 will weigh about one and a half tons. * * As the front wheels (all 

 the wheels being of the same diameter) are so large, the wagon will 

 require a large space to turn in ; but this is no objection, as it will not 

 be necessary to turn the w^agon except at the ends of the road, where 

 there will be ample room, and the wagon can be turned sufficiently to 

 pass teams on the road back to the mine." 



It will be seen that Mr. Smith's experiments have been made on level 

 surfaces. Allowance must of course be made for the undulations of 

 plank roads. The plank road from Detroit to Lansing is so graded that 

 no inclined plane of the road exceeds four feet to one hundred feet. 

 Over such roads it is practicable for a pair of hoi-ses to di-aw a load, in 

 a common wagon, of four tons, exclusive of the weight of the wagon, 

 at a working speed of two and a half miles per hour. This has been 

 found to be a practical load on such plank road gi-ades, both in Canada 

 and the State of New York. It is beginning to be practiced in this 

 State, where the construction of the common wagon is of suflScient 

 strength to bear the load. It is therefore ceilainly safe to assume that 

 a larger load can be drawii by the force of two horses over plank roads 

 so graded, on a wagon constructed for the pui-pose, with the greatly in- 

 creased power afforded by wheels of seven feet diameter and anti-fric- 

 tion axles. But I have based the subjoined estimate upon a load of 

 only four tons, on the improved wagon. The Cedar River Mine is distant 

 10 miles from Detroit, by the plank road. It is not claimed that coal, in 

 loads of four tons, on an estimate of its value at $3 per ton in Detroit, can 



