All principal parts of engine accurately fitted to gauges and thoroughly interchangeable. All movable bolts and nuts and all wearing surfaces made of steel or iron case-hardened. All wearing brasses made of ingot copper and tin, alloyed in the proportion of seven parts of the former to one of the latter. All bolts and threads to U. S. standard. TENDER. On two four-wheeled trucks. Wheels of best plate pattern, thirty inches in diameter. Truck frames of square wrought-iron with equalizers between springs, or of bar-iron with wooden bolsters. Axles of best hammered iron. Oil-tight boxes with brass bearings. Tank put together with angle iron corners and strongly braced. Top and bottom plates of No. 6 iron; side plates of No. 8 iron. Tender frame of wood or iron. PAINTING. Engine and tender to be well painted and varnished. [Transcriber's notes: Obvious printer's errors have been corrected, all other inconsistencies are as in the original. The author's spelling has been maintained. V[] is used to mark square roots; e.g.: V[6 + 1] means the square root of 6 + 1.]