The language used in the source document has been retained (including inconsistent, archaic and unusual spelling, hyphenation and capitalisation), except as mentioned below. In particular, non-English words and phrases have not been corrected unless mentioned under “Changes made”.

The (minor) deviations in spelling in the Index compared to the text have not been standardised.

Depending on the hard- and software used and their settings, not all elements may display as intended.

Discrepancies between illustrations and their descriptions (e.g., Fig. 1B in Chapter L) have not been rectified unless listed below. Items that cannot work as described (e.g. the rotating target in Chapter XX) have not been corrected or explicitly noted. Possibly offensive language (e.g. in the minstrel entertainment) and dangerous activities (as the experiments with hydrogen and chlorine gas) have been included in this transcription without further explicit warning.

Page 119, the David: as printed in the source document.

Page 184, The space, D, G, is also invisible: possibly an error for The space, D, C, is also invisible.

Page 216, The code for playing cards ...: the intended meaning of the suits (clubs and spades) given and the explanation (well and very well) in the text contradict each other.

Page 238. Fig. 9: the illustration may have been printed upside-down (cf. Fig. 10 and the text).

Page 295, various combinations of wines and liquids: as printed in the source document. Possibly an error for wires and liquids.

Page 458: It is not clear why One-blank is not listed.

Page 522, Figs. 7 and 8: The illusion “the standing pins” may not work in all formats; the bottom part of Fig. 8 has been added because it may be impossible to see the solution according to the directions given when reading this e-text.

Changes made

The (single) footnote has been moved to the end of the chapter.

Some minor obvious typographical and punctuation errors and misprints have been corrected silently.

Page 65: emotional parts of thumping changed to emotional parts or thumping.

Page 214: closing bracket added after the last two responses by the professor.

Page 257: The complete illustration consisting of Figs. 10-12 has been flipped horizontally, as have the individual figures.

Page 295: ‘the coil has been mentioned’ changed to ‘the coin has been mentioned’.

Page 438: reference to Fig. 2 changed to reference to Fig. 3.

Page 475: CHAPTER LVIX changed to CHAPTER LIX.