His research in physics, particularly on evaporation, earned him recognition and a place as the 26th member of the Royal Swedish Academy of Sciences in 1739.
Wallerius's work focuses on whether and how evaporation occurs in open or vacuumed environments, conducting experiments that ranged from observing the weight loss of an egg over an entire year or how long a cup of wine from the Rhine region evaporated, to large scale sealed copper tanks filled with various fluids observed over time.
[3] [4] Wallerius was a devout religious man who, while influenced by the enlightened time he was living in, viewed many of his younger colleagues' liberal beliefs as a threat to religion.
Wallerius actively participated in over 200 disputations both of his own works and by others where he often rhetorically attacked those who showed too much enlightened view on science and theology.
[5] When Emanuel Swedenborg was asked after the death of Nils Wallerius in 1764 what he thought the professor was doing in heaven he replied "He still goes about and holds disputations".