ERRATA, &c. 
Page 155 line 3 from bottom, omit = at the end. 
„ 158 Tredgold has made use of the moment of the pressure of the steam instead of the actual 
pressure on the parts. 
The force at the distance x from E is fy d x, which multiplied into 2 tt (r + x), the space 
described, gives 2 fnydx (r -f- x) ; and the integral is/V a y (2 r + «), the power expended 
on each revolution. It is hence plain that no power is lost, the factor nay (2 r + a) being 
the volume of steam employed at the pressure/. 
„ 1641 
jgg j Arts. 333, 342, foot-notes and other parts depending on the same, are incorrect in principle. 
The greatest effect is generally produced with the least velocity; the effect being the 
effective force multiplied into the space through which it is exerted. 
,, 263 line 11 from bottom, for second read minute. 
„ 393 lines 4 and 5 from bottom, transpose lxii. and lxiii. 
APPENDIX. 
Page 128 at the bottom on the left, for r a 3 sin. /3 read 2 r a? sin. /3. 
Plate xi. The adjustment of the parallel motion is wrong ; the same radius bar will not do for both 
ends of the beam. In the plate, the motions for the cylinders and air pump are correct; but 
the pump rods on the left cannot move in straight lines with such an arrangement. 
We are indebted to Professor Willis, of Cambridge, for a notice of this error.