Page 175: ... told me had had supplied all the money ... changed to ... told me he had supplied all the money .... Page 287: ... this they had been keen kept in ignorance of ... changed to ... this they had been kept in ignorance of .... Page 294: b′ and c′ in the text changed to b¹ and c¹ as in the illustration. Page 303: ... to very the speed ... changed to ... to vary the speed .... Page 331: ... before I left planning a smaller engine ... changed to ... before I left, planning a smaller engine .... Page 333: closing quote mark inserted after ... employing six typewriters.