Old English hwilc (West Saxon) "which," short for hwi-lic "of what form," from Proto-Germanic *khwilikaz (cf. Old Saxon hwilik , Old Norse hvelikr , Swedish vilken , Old Frisian hwelik , Middle Dutch wilk , Dutch welk , Old High German hwelich , German welch , Gothic hvileiks "which"), from *khwi- "who" (see who ) + *likan "body, form" (cf. Old English lic "body;" see like (adj.)). In Middle English used as a relative pronoun where Modern English would use who , as still in the Lord's Prayer. Old English also had parallel forms hwelc and hwylc , which disappeared 15c.
When William Smith and Sir Charles Lyell first recognized that rock strata represented successive time periods, time scales could be estimated only very imprecisely since estimates of rates of change were uncertain. While creationists had been proposing dates of around six or seven thousand years for the age of Earth based on the Bible , early geologists were suggesting millions of years for geologic periods, and some were even suggesting a virtually infinite age for Earth. [ citation needed ] Geologists and paleontologists constructed the geologic table based on the relative positions of different strata and fossils, and estimated the time scales based on studying rates of various kinds of weathering , erosion , sedimentation , and lithification . Until the discovery of radioactivity in 1896 and the development of its geological applications through radiometric dating during the first half of the 20th century, the ages of various rock strata and the age of Earth were the subject of considerable debate.