James Gregory was a Scottish mathematician and astronomer born in 1638. He is best known for his work in calculus and for developing the Gregory series, which is a way to represent functions as infinite series. Gregory also made significant contributions to the field of optics and is credited with inventing the Gregorian telescope, an early type of reflecting telescope that improved upon existing designs. In addition to his mathematical achievements, Gregory was a professor at the University of Edinburgh and later at the University of St Andrews. His work laid the groundwork for future mathematicians and scientists, influencing the development of calculus and astronomy in the years that followed.