About the year 1757 he was appointed tutor to the only son of Count Adolf Frederick Stackelberg, a situation which he filled greatly to the satisfaction both of the father and son, as long as the young count stood in need of an instructor. He took his master's degree in 1758, choosing for the subject of his thesis on _astronomical interpolation_. Soon after, he was appointed _magister docens_ in natural philosophy, a situation peculiar to the University of Upsala, and constituting a kind of assistant to the professor. For his promotion to this situation he was obliged to M. Ferner, who saw how well qualified he was for it, and how beneficial his labours would be to the University of Upsala. In 1761 he was appointed _adjunct_ in mathematics and physics, which, I presume, means that he was raised to the rank of an associate with the professor of these branches of science. In this situation it was his business to teach these sciences to the students of Upsala, a task for which he was exceedingly well fitted. During this period he published various tracts on different branches of physical science, particularly on the _rainbow_, the crepuscula, the aurora-borealis, the electrical phenomena of Iceland spar, and of the tourmalin. We find his name among the astronomers who observed the first transit of Venus over the sun, in 1761, whose results deserve the greatest confidence.[1] His observations on the electricity of the tourmalin are important. It was he that first established the true laws that regulate these curious phenomena. [1] See Phil. Trans., vol. lii. p. 227, and vol. lvi. p. 85.