some camp members were assigned specific tasks. william clayton was appointed company scribe and was expected to record an accurate description of their journey and the distance they traveled each day. after three weeks, clayton grew tired of personally counting the revolutions of a wagon wheel and computing the day's distance by multiplying the count by the wheel's circumference. after consulting with orson pratt, an accomplished mathematician, he designed a mechanism consisting of a set of wooden cog wheels attached to the hub of a wagon wheel, with the mechanism "counting" or recording by position the revolutions of the wheel. clayton's design, which he called the "roadometer", is the basis for most modern odometers. the apparatus was built to clayton and pratt's specifications by the company's carpenter appleton milo harmon and was first used on the morning of may 12, 1847. the "roadometer" showed that the company averaged between fourteen and twenty miles per day. apostle orson pratt was named the company's scientific observer. he made regular readings on scientific instruments, took notes on geological formations and mineral resources, and described plants and animals. journals kept by both clayton and pratt have become valuable resources for historians of the mormon trek west.