[Transcriber’s Note: the following changes have been made to this text.
- Page 69—added missing word “to”: “from five to seven”
- Page 101—“form” changed to “from”: “drop them from its”
- Fig. 33 caption—“arius” changed to “anus”: “and the anus,”
- Page 166—“disburb” changed to “disturb”: “to disturb him”
- Page 188—“hyrodgen” changed to “hydrogen”: “twelve atoms of hydrogen”
- Page 197—“microsope” changed to “microscope”: “under our microscope”
- Page 234—“Herschell” changed to “Herschel”: “Herschel declared that”
- Fig. 65 caption—“Fig. 64” changed to “Fig. 65”: “Fig. 65 gives the actual”
- Page 379—“Arriège” changed to “Ariège”: “Mas d’Azil (Ariège)”
- Page 391—“Predmont” changed to “Predmost”: “as at Predmost”
- Page 394—“Predmort” changed to “Predmost”: “found at Predmost”
- Page 423—“Throughton” changed to “Troughton”: “Troughton, use of spider’s lines”]